# How common is DNA testing in murder trials? \[not post-conviction DNA testing\] **URL:** \ **Category:** Factual Questions\ **Created:** [January 16, 2010, 4:48pm UTC](https://boards.straightdope.com/t/how-common-is-dna-testing-in-murder-trials-not-post-conviction-dna-testing/525204 "2010-01-16T16:48:17Z")\ **Posts on this page:** 13\ **Page:** 1
**Author:** ![Pray\_for\_peace](https://avatars.discourse-cdn.com/v4/letter/p/5f9b8f/32.png) [@Pray\_for\_peace](https://boards.straightdope.com/u/Pray_for_peace)\ **Post date:** [January 16, 2010, 4:48pm UTC](https://boards.straightdope.com/t/how-common-is-dna-testing-in-murder-trials-not-post-conviction-dna-testing/525204/1 "2010-01-16T16:48:17Z")
No, I don’t need an answer fast. 😛 In the threads on [thread=547435]What happened to JonBenet Ramsey[/thread] and [thread=547111]Overturning a wrongful conviction based on DNA evidence[/thread], there was a lot of discussion about the fact-specific nature of DNA evidence in a murder case (e.g., the relevance or weight of the evidence depends, for example, on whether the DNA was located under the victim’s fingernails or simply present somewhere at the scene). It’s my understanding that DNA testing is routine now. So, is DNA testing always done in murder cases in the US where the identity of the murderer is at issue\*\*, and the facts are such that DNA would not be exculpatory on its own, but might be a factor that a jury would consider relevant in determining reasonable doubt? Are there some states that do not have an adequate budget for testing or otherwise choose not to do DNA testing in all murder cases where the identity of the murderer is at issue? Is there a due process type argument that DNA testing should be done in a murder case? (\*\*I can imagine that DNA testing would not be necessary if the murderer was caught in the act on videotape, but I assume cases like that would be rare). ---
**Author:** ![engineer\_comp\_geek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/engineer_comp_geek/32/504_2.png) [@engineer\_comp\_geek](https://boards.straightdope.com/u/engineer_comp_geek)\ **Post date:** [January 16, 2010, 7:33pm UTC](https://boards.straightdope.com/t/how-common-is-dna-testing-in-murder-trials-not-post-conviction-dna-testing/525204/2 "2010-01-16T19:33:32Z")
My information might be a bit dated, but several years ago I saw an interview with a lawyer on this exact subject. The lawyer stated that DNA testing (at least back then) wasn’t just routinely done, because the cost made it impractical and would have driven many smaller jurisdictions into bankruptcy. This caused problems in this particular case because DNA testing hadn’t been done, and the jury was under the same impression that you are, that DNA testing had become routine. Since DNA testing hadn’t been done, the jury took it to mean that the prosecution didn’t have a strong case and found the defendant not guilty. This was several years ago, though. DNA testing might be cheaper and more commonplace now. ---
**Author:** ![Pray\_for\_peace](https://avatars.discourse-cdn.com/v4/letter/p/5f9b8f/32.png) [@Pray\_for\_peace](https://boards.straightdope.com/u/Pray_for_peace)\ **Post date:** [January 18, 2010, 2:55am UTC](https://boards.straightdope.com/t/how-common-is-dna-testing-in-murder-trials-not-post-conviction-dna-testing/525204/3 "2010-01-18T02:55:16Z")
Yes, that’s the kind of information I was looking for. I found a couple of semi-relevant cites, but I was hoping for some statistics or a more detailed answer. [A 2008 Nature article](http://www.nature.com/scitable/topicpage/Forensics-DNA-Fingerprinting-and-CODIS-736) refers to an “enormous” DNA analysis backlog in the US: > [@](#): > > However, contrary to how DNA analysis is portrayed on popular television shows, DNA samples are not analyzed within the course of an hour. Rather, the U.S. currently has an enormous backlog of samples waiting to be typed and entered into the database. Some of these samples are from cases that have outlasted their statutes of limitation, so even if these samples could help solve a crime, the crime can no longer be tried. [An October 2008 NYT article](http://www.nytimes.com/2008/10/25/us/25dna.html?pagewanted=1&_r=1) re: a backlog in DNA testing in various jurisdictions makes a couple of interesting points: > [@](#): > > About 95 percent of state and local criminal cases are resolved through plea agreements, often before DNA analyses are completed. The police and prosecutors rely on confessions, witness testimony and physical evidence like fingerprints and ballistics. … > [@](#): > > The [edit: DNA backlog] problem seems most severe here in Los Angeles, where the Police Department has the largest known backlog, about 7,000 cases, including many with rape kits from sexual assaults. > … > An audit released Monday by the Los Angeles city comptroller found that 217 backlogged cases here involved sexual assaults so old the 10-year statute of limitations had lapsed. The audit did not determine how many, if any, of those cases might have been prosecuted based on other evidence. The federal government has not quantified the country’s overall DNA evidence backlog since 2003, when it stood at 542,000 cases, but a researcher for Human Rights Watch who has studied the backlog, Sarah Tofte, estimates that it exceeds 400,000. … > [@](#): > > Pete Marone, chairman of the Consortium of Forensic Science Organizations and director of the Virginia state crime lab, said staffing levels at crime labs had not kept pace with technological advances in DNA analysis. > > “Police are starting to send us new work that we couldn’t have done before,” Mr. Marone said. “We can do ‘touch’ evidence now, utilizing DNA analysis to see whether a defendant even touched a weapon. We can get DNA evidence from steering wheels. We can go into a room and find drugs on the floor and we’ll be able to analyze those drugs to determine which hand threw them down on the floor.” ---
**Author:** ![Tim\_T-Bonham.net](https://avatars.discourse-cdn.com/v4/letter/t/46a35a/32.png) [@Tim\_T-Bonham.net](https://boards.straightdope.com/u/Tim_T-Bonham.net)\ **Post date:** [January 19, 2010, 1:27am UTC](https://boards.straightdope.com/t/how-common-is-dna-testing-in-murder-trials-not-post-conviction-dna-testing/525204/4 "2010-01-19T01:27:24Z")
According to a friend at the Minneapolis Police lab, DNA testing is: - expensive - takes a long time - uses up limited lab resources So in actual practice, it’s done only when it’s needed to solve the crime, or is needed by the prosecutor in court. Both of those are not all that common. The long delay for DNA results means that most crimes are solved before that. And in most court cases, the prosecutor has enough evidence to convince a jury without DNA (and no risk that the defense and raise questions about the DNA and confuse the jury). * * * A now-retired cop told me that from his long experience, most murders are fairly simple to solve: - 65% is the romantic partner (spouse, domestic partner, boyfriend/girlfriend, ex-spouse). - 15-20% is the heir. - 10-15% is someone the victim has been openly feuding with for a while (neighbor, annoying co-worker, competitor at work, boss at work, your girlfriend’s previous boyfriend, unpaid bookie or drug dealer, etc.) - 2-3% is a criminal doing a crime (mugger, store robber, car hijacker) – usually semi-accidental (not planned). - leaving only a very few that are really hard to solve – victim picked at random, psychopathic or serial killer, etc. ---
**Author:** ![Bijou\_Drains](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bijou_drains/32/2814_2.png) [@Bijou\_Drains](https://boards.straightdope.com/u/Bijou_Drains)\ **Post date:** [January 19, 2010, 1:33am UTC](https://boards.straightdope.com/t/how-common-is-dna-testing-in-murder-trials-not-post-conviction-dna-testing/525204/5 "2010-01-19T01:33:20Z")
Yes, the odds are very high that the murderer knows the victim or is a relative. The leading cause of death for pregnant women is murder. (that’s a bit biased since so few pregnant women die) ---
**Author:** ![Markxxx](https://avatars.discourse-cdn.com/v4/letter/m/5daacb/32.png) [@Markxxx](https://boards.straightdope.com/u/Markxxx)\ **Post date:** [January 19, 2010, 1:34am UTC](https://boards.straightdope.com/t/how-common-is-dna-testing-in-murder-trials-not-post-conviction-dna-testing/525204/6 "2010-01-19T01:34:28Z")
Well with DNA sampling money talks. True there are a lot of backlogs but it’s DNA is do-able very quickly if you pay for it. I’ve read books with cold cases in Chicago and NYC and the DNA testing is last on the list. Why? Because a 20 year old crime isn’t really that urgent, but the dectives try to come up with money to test and go to private agencies and get it done within a day or so. Of course they are paying ten times the cost. The defense can also offer to pay for it in a private setting and get it done ASAP. And it’s not just criminals. In the book “The Virus Hunters,” when West Nile Virus entered the USA the CDA and other government agencies both local, state and federal all refused to belive it was West Nile. It was diagnoses as St Louis Encephalitis. No one understood how West Nile just “jumped” to NYC without anywhere in between But the lead researcher was friends with a head guy at a military base that did testing and got it pushed through and in two days solved the mystery. It was West Nile and people were treated and many lives were saved by this researcher that had good connections with the military. ---
**Author:** ![Bijou\_Drains](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bijou_drains/32/2814_2.png) [@Bijou\_Drains](https://boards.straightdope.com/u/Bijou_Drains)\ **Post date:** [January 19, 2010, 1:39am UTC](https://boards.straightdope.com/t/how-common-is-dna-testing-in-murder-trials-not-post-conviction-dna-testing/525204/7 "2010-01-19T01:39:56Z")
The DNA labs are all booked up with tests for Maury’s guests. 🙂 ---
**Author:** ![Pray\_for\_peace](https://avatars.discourse-cdn.com/v4/letter/p/5f9b8f/32.png) [@Pray\_for\_peace](https://boards.straightdope.com/u/Pray_for_peace)\ **Post date:** [January 19, 2010, 2:18am UTC](https://boards.straightdope.com/t/how-common-is-dna-testing-in-murder-trials-not-post-conviction-dna-testing/525204/8 "2010-01-19T02:18:11Z")
> [@Bijou\_Drains](#): > > The DNA labs are all booked up with tests for Maury’s guests. 🙂 😃 Right!!! ---
**Author:** ![Pray\_for\_peace](https://avatars.discourse-cdn.com/v4/letter/p/5f9b8f/32.png) [@Pray\_for\_peace](https://boards.straightdope.com/u/Pray_for_peace)\ **Post date:** [January 19, 2010, 2:30am UTC](https://boards.straightdope.com/t/how-common-is-dna-testing-in-murder-trials-not-post-conviction-dna-testing/525204/9 "2010-01-19T02:30:22Z")
Suppose that the prosecution and/or defense wants DNA testing to be done, but there is a backlog at the lab. Does that mean that the the testing does not get done in a timely manner, and the trial just goes on without the DNA? Or would this be grounds for delaying a trial? ---
**Author:** ![Diogenes\_the\_Cynic](https://avatars.discourse-cdn.com/v4/letter/d/e99b99/32.png) [@Diogenes\_the\_Cynic](https://boards.straightdope.com/u/Diogenes_the_Cynic)\ **Post date:** [January 19, 2010, 2:37am UTC](https://boards.straightdope.com/t/how-common-is-dna-testing-in-murder-trials-not-post-conviction-dna-testing/525204/10 "2010-01-19T02:37:26Z")
If the prosecution doesn’t think the DNA will help them (meaning won’t help their case, not meaning won’t help solve the crime), they won’t pay to have it done. In that case, the defense has to pay for its own testing, which it generally can’t do. ---
**Author:** ![Pray\_for\_peace](https://avatars.discourse-cdn.com/v4/letter/p/5f9b8f/32.png) [@Pray\_for\_peace](https://boards.straightdope.com/u/Pray_for_peace)\ **Post date:** [January 19, 2010, 2:53am UTC](https://boards.straightdope.com/t/how-common-is-dna-testing-in-murder-trials-not-post-conviction-dna-testing/525204/11 "2010-01-19T02:53:47Z")
You are making a good point; someone who is relying on a public defender is not going to have access to funds for DNA testing. But there must be a range in the financial resources of defendants between those relying on a public defender and those who have O.J.-like resources or publicity. The NYT article that I linked above said > [@](#): > > If DNA is found, a chemical process creates billions of copies. A machine then produces a profile of 13 unique markers, which are entered into state and national databases for matches. Each DNA sample costs about $1,500 to analyze, criminalists said. That’s expensive, but not so expensive as to be prohibitive to any non-celebrity person. ---
**Author:** ![Tim\_T-Bonham.net](https://avatars.discourse-cdn.com/v4/letter/t/46a35a/32.png) [@Tim\_T-Bonham.net](https://boards.straightdope.com/u/Tim_T-Bonham.net)\ **Post date:** [January 19, 2010, 3:25am UTC](https://boards.straightdope.com/t/how-common-is-dna-testing-in-murder-trials-not-post-conviction-dna-testing/525204/12 "2010-01-19T03:25:42Z")
> [@Sidney Evgeni Jordan](#): > > Suppose that the prosecution and/or defense wants DNA testing to be done, but there is a backlog at the lab. Does that mean that the the testing does not get done in a timely manner, and the trial just goes on without the DNA? Or would this be grounds for delaying a trial? As Diogenes said, if it’s the defense that wants it, they can pay to have it done at a private lab. If the prosecution thinks it will help their case, they put pressure on the lab to move this testing to the front of the queue, so that it’s done in time. I suppose they could also request a delay. But this doesn’t happen much. If they already have a trial scheduled, then the prosecution must have solved the crime, and must already have enough evidence to think they can convict the accused, and enough evidence to have convinced the grand jury to return an indictment. So they’ve gone this far without the DNA evidence – they probably don’t really need it for the trial. ---
**Author:** ![Pray\_for\_peace](https://avatars.discourse-cdn.com/v4/letter/p/5f9b8f/32.png) [@Pray\_for\_peace](https://boards.straightdope.com/u/Pray_for_peace)\ **Post date:** [January 19, 2010, 7:37pm UTC](https://boards.straightdope.com/t/how-common-is-dna-testing-in-murder-trials-not-post-conviction-dna-testing/525204/13 "2010-01-19T19:37:06Z")
Right. I understand what you are saying,\*\* t-bonham\*\*. If you look at DNA as one type of evidence that can exclude a wrongly accused person, I’m surprised that the default appears to be not testing for DNA, in light of the prosecutor’s duty to pursue justice, not just be an advocate for the state. But if I understand correctly, [the US Supreme Court has found no constitutional due process right to DNA testing post-conviction](http://www.npr.org/templates/story/story.php?storyId=105646724), which is a more compelling circumstance, so to some extent it shouldn’t be a surprise that DNA testing is generally not done during the initial trial. As has been pointed out, DNA testing is not monolithic. Sometimes it’s not clear whether the source of the DNA is linked to the crime. Two experts might disagree about the proper interpretation of DNA testing results. And it’s possible that a jury might place undue emphasis on the DNA evidence and exclude or discount other evidence that tends to implicate the defendant.