DragonAsh, by way of F-P, was talking about evidence with only 50% reliability. Your lengthy example completely misses this point, and is therefore irrelevant.
Unless the insurance company is only 50% sure that the policy was taken out by Mac on the dead man, I don’t see how this fits the scenario. A better example would be if the dead man’s wife took out a million dollar policy, and Mac’s secretary has suspected Mac of having an affair with her. She has no evidence besides her hunch, and when police press her, she admits that she’s somehow only 50% hunchy about the affair. Police now have an unreliable, tenuous connection between Mac and the insurance policy.
Or, let’s say Mac fell asleep at some point and is only 50/50 on whether he was reading or sleeping.
Again, only relevant if the EZ-Pass company has vague records. A better example would be if an NJDOT worker comes forward saying he has video proof of Mac’s car crossing the bridge. They hand the video evidence to a visual CSI expert who can only say that there’s a 50% chance the car is Mac’s. He’s just not very sure, because the video is blurry and Mac’s car isn’t very distinct.
Better would be if the forensic scientist is only 50% certain that the knife matches the murder weapon. The wounds weren’t clean, and he thinks it might be the knife, but he’s only 50% sure. There’s no blood on it, so it might just be a random knife.
Two witnesses see the men arguing, one picks Mac out of a lineup, the other chooses one of the stand-ins. The police combine this eyewitness testimony and decide that they’re only 50% sure that the guy arguing with the dead man was Mac. They’re not even sure if the dead man was there, or if it was just two guys arguing.
Standing alone, each example I gave to match F-P’s 50% hypothesis is garbage. Nothing more than curiosities. Just because the police have 5 or 6 pieces of garbage doesn’t mean they have a case. It just means they’re excellent at collecting pieces of garbage. However, DragonAsh’s point was that it’s very easy to fall into the trap of thinking that all those pieces of garbage add up to something. They do not.
And therein lies the problem: they should not be. As witness the Laurie Bembenek case, arguably the most egregious example of circumstantial evidence used to prosecute someone in recent memory.
As to your hypothetical example, the question a defense attorney might raise (and a jury might ponder):
[ol]
[li]Was Max’s knife the murder weapon? If the police found such a knife in his possession, they would have had it analyzed for traces of blood. The absense of any such blood would definitely blow the case wide open.[/li][li]Do we know that it was Max who drove his car through the toll bridge at 1 a.m.? If the defense produces a third party who testifies that they borrowed Max’s car that night, Good-bye Ruby Tuesday.[/li][li]Eyewitness testimony has been shown, especially in recent years, to be unreliable. This witness does not even positively identify Max at the scene. How can she be sure the trenchcoat is beige? How can she be sure he walked with a limp?[/li][/ol]
Max would be home in time for Dancing With The Stars.
I disagree. If the jury is reasonably confident that the defendant is guilty, then he should be convicted.
[quote]
[li]Was Max’s knife the murder weapon? If the police found such a knife in his possession, they would have had it analyzed for traces of blood. The absense of any such blood would definitely blow the case wide open.[/li][/quote]
I agree, but so what?
Again I agree, but so what?
The same way anyone is sure of anything else they have witnessed in their life.
None of this changes the basic fact that situations can and do arise where one can be reasonably confident about a certain conclusion based on numerous pieces of evidence each of which considered in isolation is inconclusive.
ETA: Would you mind pointing to a few recent, prominent murder convictions where (1) the defendant insisted on his innocence; and (2) you are still reasonably confident the defendant was guilty?
For example, if the likelihood that the victim’s DNA would end up on the knife from contamination is 50%, and the victim’s DNA was found on five different knives in different locations (i.e. we are hypothesizing 5 different contaminations), then that’s a good indicator that they are not all there from contamination - the likelihood that all were due to contamination would be 1/32.
Looking at each one and dismissing it without consideration of the others is a logical error.
Can you explain exactly what you mean by “50% reliability” so I know we are both on the same page?
And, are you denying that situations can and do arise where one can be reasonably confident about a certain conclusion based on numerous pieces of evidence each of which considered in isolation is inconclusive?
Lol, no. I made a statement based on my general knowledge, observations, experience, and common sense. Just like I do not have a cite for the claim that Mongolian men are in general taller than Mongolian women but I nonetheless believe it to be so even without looking for studies on the issue.
You denied that it’s rare for a person to be unable to give a coherent account of his actions and whereabouts. Which implies you think it’s common. So I am asking you to give me some examples.
You’re doing it again. ‘Once would be a coincidence, but not all five! This can’t be a coincidence!’
You can’t group all five together and say the whole is more credible than any individual piece - not when there’s a 50% chance that any individual piece of evidence is worthless.
I hope you’re never allowed anywhere near a jury trial.
[FWIW, I believe Occam’s Razor operates on a similar if not identical principle, but I’m not going to get bogged down in arguing about OR. At any rate what I’ve written is basic logic.]
I allowed a couple of comments like this earlier in the thread, but I’m going to say now that it’s off limits. Commenting on a poster’s argument and its implications is fine, but when there’s too much commentary on what the argument says about the person, it’s a short step to flaming. No more of this, please. And the same goes for this:
And Snowboarder Bo, I admit I asked the same question Gary Kumquat did upthread, but I’m instructing you to just answer it. You’re not even being asked to defend an argument, you’re being asked to explain the basis for your opinion and I can’t think of a good reason you are refusing to post that.
I agree. If there is a piece of evidence which, standing alone, means there is a 50/50 chance which the Defendant is guilty. And there are 4 other (independent) pieces of such evidence, then it’s very very likely that the Defendant is guilty.
Consider DNA evidence. For the sake of simplicity, think about a paternity test although the same principle applies to any DNA test.
When they give you a paternity test, they match 20 or 30 of the putative father’s alleles against those of the child. The chances of 1 allele matching just by chance are actually pretty good. But the chances of 20 or 30 matching just by chance are astronomically low. So that the chances the putative father is the actual father become quite high.
It seems that using the logic of DragonAsh, one could consider each of the allele matches in isolation and dismiss each one in turn and never reach any conclusion.
It’s worth keeping in mind that almost all evidence is ambiguous. Almost all the time, one can come up with plausible ways to explain away and dismiss any single piece of evidence. Which is why I asked another poster to identify a few prominent murder convictions where he was reasonably confident of the defendant’s guilt despite the defendant’s protestations of innocence.
Here’s the problem. We’re not talking about evidence that standing alone shows that there’s a 50-50 chance that the defendant is guilty. We’re talking about evidence about which we’re only 50 percent sure that that piece of evidence is true at all.
Again, we’re not talking about evidence whose *implications *are ambiguous. We’re talking about evidence that in and of itself is not sufficiently credible to qualify as evidence at all.
On the one hand you have DNA testing that produces a result that there is a 80 percent chance that Dude A is the father. On the other hand, you show that the DNA lab workers’ handling of the evidence was so bad, that we don’t even know whether they tested the DNA found at the scene of the crime or whether they smeared DNA found somewhere else all over the laboratory. There’s a huge difference. That 80 percent result no longer counts as 80 percent. It very well might count as nothing at all.
“50% reliability” wasn’t my terminology, and I think putting a number on evidence that lacks reliability or credibility is a bit contrived. I tried to come up with some examples where things were “50% reliable,” and can extend that to things such as DNA evidence that’s a 50% match (not particularly good). The important thing is to acknowledge that there’s a difference between conclusive yet indirect (to steal the word from upthread) evidence, and junk evidence. The former would be EZ-Pass records that conclusively prove the suspect’s car was at x location at y time, while not conclusively proving that the suspect was in the car. In isolation it’s not a slam dunk, but it can help build a case. The latter would be a co-worker with an ax to grind saying he heard the suspect plotting the crime in the bathroom one day. I’m sure the prosecution would call the co-worker to testify and let the jury determine the credibility of the witness, but if that type of testimony is all that the prosecution had brought to the table, I’d hope that the jury would see through it and realize there wasn’t a case.
Sure, it’s called the preponderance of evidence, right? What matters is that the individual pieces of evidence are credible. If everyone in the high school says that Sally is a tramp, it must be true, right? Because everyone says it. One person says it, it could just be a grudge, but if everyone says it, well, tramp she she is, right? Or maybe we should sit down with every single high-schooler and figure out if they’re basing their accusations on anything more than rumor. If not, we should throw out the whole lot, no matter how many there are.
As noted earlier, this is a distinction without a difference (for our purposes).
For some reason, you’ve declined to address this and explain why you think this distinction matters.
ETA: the bottom line of both situations is that the likelihood that a series of unrelated plausible events took place is less than the likelihood that any one of them took place.
The error here is that the various people saying it in this case are not unrelated. A lot of these people are basing their opinions on the other people who say it. So it’s all one piece of evidence of shaky value.
You can’t compare that to a series of unrelated pieces of evidence.