Statistics say he did it, Do you convict?

[treis]

Lets say that you are a hypothetical juror hearing a murder case. The victim in question is a 24 year old, pregnant, recently estranged from her boyfriend that is the father of the child. No body was found nor was there any eyewitness or physical evidence that links the father to the murder. None the less he has been arrested and is now on trial for the crime. Lets also assume that there was a way for the father to easily have disposed of the body, say he owns a fishing boat that can travel far out onto a large lake they live on.

During the trial the prosecuter calls his one and only witness, a professor of Sociology from Generic State University. This professor has dedicated his career to studying the circumstances that surround murders. In this case he has done a meticulous study and found that in cases in which the victim is recently estranged from the father, young and pregnant the father is the murderer in 99% (or which ever number constitutes beyond a reasonable doubt to you) of the cases. The study in question is tight and the conclusions and application in the case is sound.

Lets say that this is the only evidence entered in the case and the defense basically argued that the prosecuter has not proven anything.

Is the study enough evidence for you to find the defendant guilty beyond a reasonable doubt?

To me I am very much on the fence about this case. Looking at it objectively assuming the study is sound there doesn't seem to be any reasonable doubt that he is the murderer. Why would fingerprints with a same level of confidence as the study be proof but the survey not? Both things point to the father with the same level of accuracy. However there just seems to be something wrong about using the study becuase it doesn't really show anything other than the fact that a lot of guys in the same situation have killed their ex-girlfriends. It seems wrong that a man is convicted on the sole basis of what others in a similar situation has done.

Thoughts?

[SentientMeat]

No (http://en.wikipedia.org/wiki/Prosecutor%27s_fallacy).

[Driver8]

I'd say there is plenty of reasonable doubt. I would not convict.

I guess if the study has the same reliability as fingerprint or DNA sampling my conclusion makes little sense. But I think I would find it really hard to swallow that the study was as concrete as physical evidence. One could not say there is no reasonable doubt that someone else could have done it in the absense of any physical evidence, no matter what the statistics say.

[Larry Borgia]

Besides SentientMeat's mathematical reasoning, there is a moral element to this.

When we here evidence of a case we expect to hear evidence linking the specific person to the crime.

With fingerprints the evidence says "These fingerprints are 99.9999% likely to be Joe Jones'. " With Sociological reasoning the evidence says "Murders like these are 99.9999% likely to be committed by people like Joe Jones." The first case ties the suspect specifically to the crime, the other puts the suspect in a class of people who were likely to commit the crime. A court should judge individuals, not classes. I'm sure it would not be hard to imagine cases where the hypothetical sociological reasoning could be grossly misused by the state. Especially since I don't think sociological reasoning is anywhere near as accurate IRL as in this hypothetical.

[Larry Borgia]

:smack: when we hear evidence, that is...

I keep doing stuff like this...

[Campion]

It doesn't matter what I think I would do; as a juror, I would never get the case. The prosecutor's study fails to establish the elements of the crime; having failed to make a prima facie case that this defendant committed this crime, the judge must dismiss the case.

[Larry Borgia]

It doesn't matter what I think I would do; as a juror, I would never get the case. The prosecutor's study fails to establish the elements of the crime; having failed to make a prima facie case that this defendant committed this crime, the judge must dismiss the case.

You are correct, Campion. But I think what the OP is looking for is the underlying flaw in the reasoning in his (?) hypothetical, not what an actual court would do if a prosecutor actually brought this forward with no more evidence than in the OP.

[Bricker]

As a juror, I would vote to acquit, because the prosecution failed to establish each and every element of the crime beyond a reasonable doubt.

[John Mace]

Thoughts?

I think your hypothetical is outside the realm of possibility, and so is not meaningful in any way. It's like saying: what if it were discovered that 99.99% of all people with red hair have committed murder. Should we arrest all red headed people? Nature does not work that way, so you have postulated an alternate universe in which case alternate legal rules would apply.

[Jonathan Chance]

Hell, the underlying flaw I see is that while all killers of this type are fathers etc not all fathers etc and killers.

Acquit. You're going to have to show me some specific evidence that this person was involved before I MIGHT be willing to take such evidence into account.

But maybe not.

[DrDeth]

Well, I wouldn't, but some jury's might. After all they convicted Scott peterson with not much more evidence than that. (The evidence agains him was primarily:"1 It was a really heinous crime 2. He was lying scum 3. His alibi wasn't much good and 4. Did I mention it was a really heinous crime?" :rolleyes: )

[Paul in Qatar]

No. The State has not proved a crime was committed. The State has not connected this person with this act. The State has not established Motive, Opportunity and Ability.

The defendant has no case to answer for. Deliberate to ten in the morning to get the per diem then go home.

[treis]

With fingerprints the evidence says "These fingerprints are 99.9999% likely to be Joe Jones'. " With Sociological reasoning the evidence says "Murders like these are 99.9999% likely to be committed by people like Joe Jones." The first case ties the suspect specifically to the crime, the other puts the suspect in a class of people who were likely to commit the crime. A court should judge individuals, not classes. I'm sure it would not be hard to imagine cases where the hypothetical sociological reasoning could be grossly misused by the state. Especially since I don't think sociological reasoning is anywhere near as accurate IRL as in this hypothetical.

Sure studies are not this accurate in real life but hey thats the beauty of hypotheticals ;).

I see your point about classes of people but I am not sure it applies in this situation. The study in this case does link a specific person to the crime namely the father of the baby. I guess I don't see the difference between saying the finger prints pointing 99% accurately to Joe Jones and the study (given the conditions are met) showing that Joe Jones (assuming he is the ex) to 99% accuracy.

It doesn't matter what I think I would do; as a juror, I would never get the case. The prosecutor's study fails to establish the elements of the crime; having failed to make a prima facie case that this defendant committed this crime, the judge must dismiss the case.

Why doesn't the study count as prima facie evidence that the father of the child is the murderer?

I think your hypothetical is outside the realm of possibility, and so is not meaningful in any way. It's like saying: what if it were discovered that 99.99% of all people with red hair have committed murder. Should we arrest all red headed people? Nature does not work that way, so you have postulated an alternate universe in which case alternate legal rules would apply.

Yes the scenario postulated in the OP is most likely beyond the realm of possibility but given enough specifics you can get a fairly high likelyhood. I think we ought to agree on the idealized case before we move to any real life situation.

Acquit. You're going to have to show me some specific evidence that this person was involved before I MIGHT be willing to take such evidence into account.

Why is this any less specific than say matching DNA found in a rape victim to a suspect.

Basically my line of reasonin is:

Premise: The murderer in cases like this one has a probability of 99% of being the father
Premise: The suspect is the father
Conclusion: The suspect has a 99% probability of being the murderer

How does that differ from:

Premise: The rapist in cases like these has a probability of 99% of being the person whos sperm is found in the victim
Premise: The suspect's sperm was found in the victim
Conclusion: The suspect has a 99% probability of being the rapist.

Replace 99% with the necessary number that satisifies beyond a reasonable doubt.

As a juror, I would vote to acquit, because the prosecution failed to establish each and every element of the crime beyond a reasonable doubt.

Is this becuase no body was found? If so then go ahead and assume that a body was found. I merely said it wasn't in the OP becuase I wanted to consider only the evidence of the study and wanted to exclude evidence possibly given by the body.

No. The State has not proved a crime was committed.

Ok, assume also that the prosecuter also proved that the victim was indeed murdered.


The State has not connected this person with this act.

Sure it has by way of the study.


The State has not established Motive, Opportunity and Ability.

I wasn't aware that it necessarily had to do any of the above. Of course by proving that the defendent is guilty the prosecuter proves that there necessarily must have been the opportunity and the ability to committ the crime.

[Contrapuntal]

I see your point about classes of people but I am not sure it applies in this situation. The study in this case does link a specific person to the crime namely the father of the baby. I guess I don't see the difference between saying the finger prints pointing 99% accurately to Joe Jones and the study (given the conditions are met) showing that Joe Jones (assuming he is the ex) to 99% accuracy.

I see at least two problems. First, you are assumning that sociology and biology are equivalent disciplines; they aren't. Second, testing one person to see if he fits into a group of one is very different from testing a group of people to see who fits in it.

[vetbridge]

Not enough information in the OP to come to a conclusion.

Does the defendant have beady, little eyes that dart back and forth? That's what we need to know.

[treis]

I see at least two problems. First, you are assumning that sociology and biology are equivalent disciplines; they aren't.

That is true but this is an idealized case. Obviously no study can get that sort of accuracy and there is no way a prosecutor would end his case there. I guess the fundamental question underlying all of this is how much weight, if any, should we give to studies like this.


Second, testing one person to see if he fits into a group of one is very different from testing a group of people to see who fits in it.

I don't think I fully understand this objection.

Not enough information in the OP to come to a conclusion.

Does the defendant have beady, little eyes that dart back and forth? That's what we need to know.

Unfortunately for the defendent he lost both eyes in a freak chalupa accident. I don't know if you can consider his glass eyes to be beady but they sure aren't darting back and forth ;)

[Campion]

You are correct, Campion. But I think what the OP is looking for is the underlying flaw in the reasoning in his (?) hypothetical, not what an actual court would do if a prosecutor actually brought this forward with no more evidence than in the OP.Ok. My issue was partly that there was no evidence to prove up fundamental elements of the crime: no evidence that the defendant knew the woman, that she was pregnant, that he was the father, that she disappeared, that he had the requisite mens rea, etc. But focusing on flaws in the study alone: as has been said before, and better, the study does does not show that this man committed a crime, just that men who are in some respects like him have committed similar crimes to the one he is accused of. (That sentence should be taken out and shot, but I'll leave that to others to do.)

Why doesn't the study count as prima facie evidence that the father of the child is the murderer? A prima facie case is one in which all the elements of the crime are proven. Whether they can be rebutted by the defense is a separate, and for purposes of this argument, irrelevant issue. But if the prosecutor cannot make a prima facie case (meeting all elements), then it doesn't matter what the study says. You would need, at a minimum, two witnesses other than the study's author: the ob-gyn (who would need to testify that she was pregnant and the defendant was the father); and the cop (who would need to testify to death, cause of death, and the defendant's opportunity).

Paul in Saudi, motive is not actually an element of the crime, but you are correct that most prosecutors will try to prove motive because the jury wants to know why he did it.

But back to the study: let's assume you've proven those predicate facts about the defendant's relationship to the victim and the baby, you've found the body, and the cop testifes that the defendant owns a boat that would permit him to go out on the water and dump a body.

Here's the primary problem: all murder statutes in the US require a specific mental state, what the law calls mens rea. That means that you must prove that the defendant himself actually had a specific intent to cause the victim's death. It isn't enough to show that other men in similar situations had the mental state, you must show that this defendant did.

Take a look at California's murder statute (http://caselaw.lp.findlaw.com/cacodes/pen/187%2D199.html):187. (a) Murder is the unlawful killing of a human being . . . with malice aforethought.

188. Such malice may be express or implied. It is express when
there is manifested a deliberate intention unlawfully to take away
the life of a fellow creature. It is implied, when no considerable
provocation appears, or when the circumstances attending the killing
show an abandoned and malignant heart.
When it is shown that the killing resulted from the intentional
doing of an act with express or implied malice as defined above, no
other mental state need be shown to establish the mental state of
malice aforethought. Neither an awareness of the obligation to act
within the general body of laws regulating society nor acting despite
such awareness is included within the definition of malice.

So the primary problem with the study is that it proves nothing about what this defendant actually did. That is why the study is not prima facie evidence that he killed her -- the study says nothing about what this defendant did. (I would also move to exclude the study as more prejudicial than probative and as improper opinion. I think I might win on that first ground.)

Is the study enough to convict the defendant in the court of public opinion? Yes. Would it stand up in a court of law? My opinion, no, not as the sole evidence of murder.

[Paul in Qatar]

So you are saying she has beany eyes?

(I know, no decent chalupa has beans, but still.)

[Contrapuntal]

I don't think I fully understand this objection. If one person has committed a crime than the set of <persons who did crime x> contains one element, the criminal. DNA or fingerprint testing attempts to identify the criminal by eliminating every person who is not part of that set. That's what the "99%" figure means. 99% of the population does not fit the profile (in this case, DNA ID or fingerprints.) Furthermore, the crime has already been committed. There is not a predictive element in DNA testing.

A sociological profile simply says that of all the cases studied involving A, the perpretrators were B 99% of the time. It predicts that when the criminal is found, he wil be B. It says nothing about any particular individual, and it says nothing about any B's who might not be the perpretrator. Your special case example where B could only be one person does nothing to change the method used to identify him, or the fact that it is a predictive one rather than a descriptive one.

[Annie-Xmas]

Statistics don't murder people. People murder people.

[Campion]

treis, by the way, interesting question. Meant to add that above.

[treis]

So the primary problem with the study is that it proves nothing about what this defendant actually did. That is why the study is not prima facie evidence that he killed her -- the study says nothing about what this defendant did. (I would also move to exclude the study as more prejudicial than probative and as improper opinion. I think I might win on that first ground.)

I agree with your objections and I suppose I should have included that stuff in the scenario. However I do believe that I (luckily) specified that the study was of murder cases and the father was the murderer in 99% of the cases.

If one person has committed a crime than the set of <persons who did crime x> contains one element, the criminal. DNA or fingerprint testing attempts to identify the criminal by eliminating every person who is not part of that set. That's what the "99%" figure means. 99% of the population does not fit the profile (in this case, DNA ID or fingerprints.) Furthermore, the crime has already been committed. There is not a predictive element in DNA testing.

A sociological profile simply says that of all the cases studied involving A, the perpretrators were B 99% of the time. It predicts that when the criminal is found, he wil be B. It says nothing about any particular individual, and it says nothing about any B's who might not be the perpretrator. Your special case example where B could only be one person does nothing to change the method used to identify him, or the fact that it is a predictive one rather than a descriptive one.

Ah yes I see your point now. However is there not some nonzero chance that the persons DNA, fingerprints or whatever were not involved in the crime? Aren't we making an underlying assumption that when those things are found there is a very high probability that the person they belong to is the guilty party? This is an assumption that we can make becuase the case history and logic in most cases come agree with that assumption. Why doesn't the study in this case establish that the assumption of the father being the murderer is correct?

In other words if we have a body and trace the DNA of the fetus back to John Doe and using assumptions justified by the survey to try him how does that differ from finding his DNA in her vagina and tracing it back to him?

Statistics don't murder people. People murder people.

And here I was thinking it was dangerious minorities!


(I aplogize for continually adding information to the scenario I guess I needed to be more clear. Thank you for your kind words Campion )

[Contrapuntal]

Ah yes I see your point now. However is there not some nonzero chance that the persons DNA, fingerprints or whatever were not involved in the crime? Aren't we making an underlying assumption that when those things are found there is a very high probability that the person they belong to is the guilty party? This is an assumption that we can make becuase the case history and logic in most cases come agree with that assumption. Why doesn't the study in this case establish that the assumption of the father being the murderer is correct?

I think you need to face up to the limitations of your hypothetical situation. Perhaps you make too much of the concept that someone was convicted "by DNA." Evidence of DNA in the vagina only puts the suspect on the scene. It does not establish guilt. Correct me if I am wrong, but you seem to have this idea that, Perry Mason style, a prosecuter can just whip out DNA test results and the trial is over. DNA does not prove rape. If a woman claims I raped her, and my defense is there was no intercourse, then a DNA test can show me to be a liar, which would weaken my defense. If my defense is the sex was consensual, then DNA alone will not convict me. Other evidence must be presented. So the existence of a positive DNA test or fingerprint match, in and of itself, is not enough to establish guilt.

Proving that someone is the father of a dead child, and presenting sociological evidence (remember, this type of evidence only predicts, it does not identify) that 99 times out 100 in such cases the father is the murderer, in and of itself is insufficient to convict anyone.

[treis]

I think you need to face up to the limitations of your hypothetical situation.

Yes it does appear that my hypothetical is lacking some very important pieces of information. I didn't provide any evidence that a murder occured nor did the prosecutor prove it. I neglected that facet of the case and the legal beagles rightly set me straight.


Perhaps you make too much of the concept that someone was convicted "by DNA." Evidence of DNA in the vagina only puts the suspect on the scene. It does not establish guilt. Correct me if I am wrong, but you seem to have this idea that, Perry Mason style, a prosecuter can just whip out DNA test results and the trial is over. DNA does not prove rape. If a woman claims I raped her, and my defense is there was no intercourse, then a DNA test can show me to be a liar, which would weaken my defense. If my defense is the sex was consensual, then DNA alone will not convict me. Other evidence must be presented. So the existence of a positive DNA test or fingerprint match, in and of itself, is not enough to establish guilt.

No but I guess I am assuming things that I explicitly need to state. I am more focused on who committed a crime and less concerned with proving that a crime actually occured. In the rape case I should have added that there were obvious signs that the victim was forced into sex and then murdered and the prosecutor had proven this to the satisfaction of the jury.


Proving that someone is the father of a dead child, and presenting sociological evidence (remember, this type of evidence only predicts, it does not identify) that 99 times out 100 in such cases the father is the murderer, in and of itself is insufficient to convict anyone.

Yes I do see that now. How about for instance the woman was found chopped up and stuffed into a barrell. Clearly this is was not an accident and by attempting to conceal the body whomever murdered her knew that they had committed a crime. Now we can agree that this new evidence would establish both that a murder occured and the murderer had a mens rea, correct?

Lets also assume that the prosecutor has successfully proved that the woman was pregnant, the defendant knew he was the father and they were estranged.

Now I believe that the necessary conditions have been satisfied that both a murder occured and the scenario satisifies the requirements for the study to apply. Is that study enough to find the defendent guilty of the crime?

[Duckster]

Anyone remember, "Court Martial," an episode of Star Trek: The Original Series? Captain Kirk stands trial on charges of negligence. The only direct evidence was the ship's computer. No one questioned the accuracy of the logs because computers are infallible, yet no one thought the computer could have been sabotaged and the logs changed.

Shall we use statistics and probability to convict people just because the accused happened to be in a particular statistical category? I think not.

[Contrapuntal]

Yes I do see that now. How about for instance the woman was found chopped up and stuffed into a barrell. Clearly this is was not an accident and by attempting to conceal the body whomever murdered her knew that they had committed a crime. Now we can agree that this new evidence would establish both that a murder occured and the murderer had a mens rea, correct?

Lets also assume that the prosecutor has successfully proved that the woman was pregnant, the defendant knew he was the father and they were estranged.

Now I believe that the necessary conditions have been satisfied that both a murder occured and the scenario satisifies the requirements for the study to apply. Is that study enough to find the defendent guilty of the crime?I am having a hard time making my point and I blame it all on my inability to make it clearly. I was hoping someone more eloquent would come along and help me out, but failing that...

It boils down to this. DNA testing excludes possible suspects, sociological studies (which in this excample is tantamount to profiling) includes them. You know the old Sherlock Holmes saying, "Whenever you haved ruled out the possible, whatever remains, no matter how improbable, is the answer"? What DNA testing attempts to do is rule out everybody but the suspect. That is where the "99%" figure comes in, although it is usually more like "99.52103%". The prosecutor will say something like "Only one in 50 million men could have committed this crime. And that, along with everything else I have shown you, leads to the conclusion that X is guilty." Proof beyond a reasonable doubt.


A sociological study, no matter how well done, is simply putting people in categories (inclusion) Depending upon how well it is done it can have predictive power, but not about individuals, only about groups. It has the potential to be evidence, I suppose, but it is not the kind of thing that offers proof.

Proof is obtained by ruling things out. Sociological studies cannot, by their nature, do that.

[treis]

Ah Contrapuntal I think I have it!

Why is it that the DNA evidence excludes possible suspects? Its becuase we have assumed that the person's semen in a woman's vagina and the blood under her finger nails is the rapist. If they do not find my semen in her does that definitively mean that I am not the rapist? Certainly not, there is a small but non-zero chance that she had engaged in consensual albeit rough sex with a person and then I raped her with a condom on. However we have assumed that absent of other evidence that the person's DNA that matches the blood and the semen is the rapist beyond a reasonable doubt.

The study that is presented in the OP is not evidence of the murder rather it is the justification for the assumptions the jury should make. The evidence in this case would be that the women is young, pregnant and estranged from her boyfriend. We then go to our study and start checking off boxes just as the jury does in a rape case and determine the verdict. Basically the jury does something like that for each case. In the rape example it would be:

Evidence of non-consual sex: Check
DNA of blood under finger nails matches the defendent: Check
DNA of semen matches the defendent: Check
Evidence meets assumptions necessary for proof beyond a reasonable doubt: Check

Verdict: Guilty

Using the study:

Evidence of a murder: Check
Victim is relatively young: Check
Victim is pregnant: Check
Victim and boyfriend are estranged: Check
Boyfriend knew he was the father: Check
Evidence meets assumptions necessary for proof beyond a reasonable doubt: Check

Verdict: Guilty

Basically all this study does is replace the logic and experience justification for a guilty assumption and replaces it with a systematic justification for a specific condition.

[pravnik]

Not enough information in the OP to come to a conclusion.

Does the defendant have beady, little eyes that dart back and forth? That's what we need to know.I certainly hope you are joking here. This should never be enough to convict someone of a crime.

He should be wringing his sweaty little hands, too.

[Mr2001]

Do I convict? No.

If you were hypothetically in charge of a fire station, would you refuse to hire women because they're statistically unlikely to have the necessary strength? The law says no. There are always exceptions, and if that's important when making hiring decisions, IMO it's a million times as important during a trial.

[treis]

Sure and the defense had a chance to offer those exceptions but chose not to.

[davenportavenger]

I certainly hope you are joking here. This should never be enough to convict someone of a crime.

He should be wringing his sweaty little hands, too.No, he needs to have the evil gene, the one shared by Hitler and Walt Disney.

I would not convict. People should be judged as individuals, not as members of a specific group. In fact, I think that if a prosecutor did bring up evidence like this, it would be cause for a mistrial, in that he was deliberately poisoning the well and trying to turn jury sentiment against the defendant, instead of bringing out the facts.

[Blalron]

I absolutely would not. Using that type of logic, you could argue that Blacks and Hispanics are more likely to commit crimes and on that basis the defendent should be found guilty.

[Mr2001]

Sure and the defense had a chance to offer those exceptions but chose not to.
The onus isn't on the defense to prove that the defendant is an exception; the prosecution's argument is invalid from square one simply because we know exceptions exist, which means there's always reasonable doubt if the only evidence they offer is a statistic.

To continue my analogy, a female applicant at the fire station shouldn't have to prove her strength any more than a man would, therefore a defendant who's part of a suspicious group shouldn't have to prove his innocence any more than someone in another group would.

[saoirse]

The wikipedia link that Sentient Meat posted is terrific, and it explains why you can't say 99% of these cases turn out to be the father, so it's 99% likely that this time it's the father.

The presumption of innocence requires that the odds of an individual being the perpetrator cannot be considered to be 1:1. Therefore, applying 0.99 to one and coming up with a 99% likelihood is a logocal fallacy. A URL=http://en.wikipedia.org/wiki/Prosecutor's_fallacy]Prosecutor's Fallacy[/URL], in fact (in case you didn't catch it the first time).

[phouka]

Absolutely not. A sociological study is good enough to convince the police to look at someone as a suspect and gather evidence, but nowhere near enough to convict someone of a crime.

[treis]

What of my assumption rationale?

[Contrapuntal]

Ah Contrapuntal Basically all this study does is replace the logic and experience justification for a guilty assumption and replaces it with a systematic justification for a specific condition.
If what you are trying to do is prove something, you cannot replace logic with anything. Without logic there is no proof. This, I believe, is where you are making your mistake. As others have suggested, read SentientMeats's link again, as well as Campions's post. The former shows why the assumption of guilt based on your "99%" study is a fallacy; the latter shows why the case would never even come to trial. The jury would never hear about the study. It is evidence of nothing at all. You need to understand this. Introducing a study about what thousands of other men have done tells you exactly zero about what I have done. There is no group of men who are identical in every way. You could find hundreds of identical traits that would include me in a particular group; there would still be thousands more traits that would exclude me.

Trials are about evidence.

[CalMeacham]

I think the legal case has been addressed above (and I know I wouldn't want to be convicted on a purely statistical argument), but read John Allen Paulos' book [B]Innumeracy, where he discusses a trial in which a statistical argument was used in an attempt to convict. Fortunately, it was blown out of the water by a more savvy defense, with a better grasp of mathematics:

http://www.amazon.com/exec/obidos/ASIN/0809058405/qid=1118154426/sr=2-1/ref=pd_bbs_b_2_1/104-5791173-8011932

[Man With a Cat]

I went to Generic State U, and i remember that guy. Called himself a "Sociology Professor", but he kept spelling Sociology with two "L''s and falling asleep in class. I wouldn't believe a word that came out of his mouth, him and his beady eyes, always wringing his hands and such.......

[42fish]

Statistics don't murder people. People murder people.

When statistics are outlawed, only 99% of outlaws will have statistics.

[Wendell Wagner]

The problem with the example in the OP is that it assumes a level of knowledge in criminology that's far, far above the level that actually exists. Indeed, it's far from the level that could ever exist, unless not just the accuracy of criminology improves but society itself changes in some weird way. There are no comparable crimes at present for which one could say that if crime X happens then Y (who is in relation Z to the victim) must with probability 99% or greater be the criminal. There are, I suppose, cases like the following: A woman is found murdered. Her estranged husband was known to be violent. Now, any competent detective is going to immediately suspect the husband. He may even, if he thinks in a mathematical way, say that in cases like this 10% or 25% or 40% of the time it does turn out to be the husband. It's not anywhere close to 100% of the time though. He's not going to immediately bring the case to a grand jury though. He's not even going to declare the husband to be the prime suspect, I think, but just a person of interest. He'll go and interview the husband and find out if he has an alibi. He'll go to the murder scene and find if there's any evidence that points to anybody specific being the murderer.

I can't think of any crime for which a criminologist could say with 99% accuracy that a person with a specific relationship must have done the crime. Even if there was such a crime, 99% accuracy isn't enough to convince a jury, I think. The problem with the situation proposed in the OP isn't that the case relies on probabilities. All court cases rely on probabilities. Even if a jury votes to convict, they realize that there is a tiny chance that they may be wrong. The problem is that criminology doesn't have the accuracy that you posit and as far as I can see will never have that accuracy.