How the “CSI effect” can obscure the limited role of DNA-based investigative leads

People have been talking about the “CSI effect” for decades.

In short, the “CSI effect” is characterized as the common impression that forensic technologies can solve crimes (and must be used to solve crimes) in less than an hour, or within the time of a one-hour television show.

When taken to its extreme, juries may ask why the law enforcement agency didn’t use advanced technological tools to solve that jaywalking case.

Advanced technological tools like DNA, which has been commonly perceived to be the tool that can solve every single crime.

Well, that and video, because video is powerful enough to secure a conviction. But that’s another story.

Can DNA result in an arrest in a Denver homicide case?

A case in point is this story from KDVR entitled “DNA in murder case sits in Denver crime lab for 11 months.”

This is a simple statement of fact, and is not that surprising a statement of fact. Many crime labs are inundated with backlogs of DNA evidence and other forensic evidence that has yet to be tested. And these backlogs ARE creating difficulties in solving crimes such as rapes.

But when you read the article itself, the simple statement of fact is painted as an abrogation of responsibility on the part of law enforcement.

A father is making an emotional plea and putting up $25,000 of his own money to help find his son’s killer.

He is also asking the Problem Solvers to look into the time it has taken for DNA evidence to be tested in this case and others.

Tom O’Keefe said it’s taking too long to get answers and justice.

From this and other statements in the article, a picture emerges of an unsolved crime that can only be solved by the magical tool of DNA. If DNA is applied to this, just like they do on TV, arrests will be made and the killer will be convicted.

So why is it taking so long to do this?

Why is justice not being served?

KDVR is apparently not run by impassioned activists, but by journalists. And it is important from a journalistic perspective to get all sides of the story. Therefore, KDVR contacted the Denver Police Department for its side of the story.

The Denver Police Department has identified all parties involved, and the investigation shows multiple handguns were fired during this incident. While this complex case remains open, which limits details we can provide, we can verify that a significant amount of forensic work has been completed, but some remains. Investigators believe the pending forensic analysis can potentially support a weapon-related charge but will not further the ongoing homicide investigation.

OK, let’s grant that they’re not trying to identify an unknown assailant, since “all parties involved” are known.

But once that DNA is tested, isn’t that going to be the magic tool that provides the police with probable cause to arrest the killer?

Um, no.

Even IF the DNA evidence DOES happen to show a significant probability that an identifiable person committed the homicide, that in itself is not sufficient reason to arrest someone.

Why not?

Because you can’t arrest someone on DNA evidence alone.

DNA evidence can provide an investigative lead, but it has to be corroborated with other evidence in order to secure an arrest and a conviction. (Don’t forget that the evidence has to result in a conviction, and in most of the United States that requires that the evidence show beyond a reasonable doubt that the person committed the crime.)

Why was a serial killer in three European countries never brought to justice, despite overwhelming DNA evidence?

Reasonable schmeasonable.

If DNA ties someone to a crime, then the person committed the crime, right?

Let’s look at the story of a serial killer who terrorized Europe for over a decade, even though ample DNA evidence was found at each of the murder scenes, beginning with this one:

In 1993, a 62-year-old woman was found dead in her house in the town of Idar-Oberstein, strangled by wire taken from a bouquet of flowers discovered near her body.

Nobody had any information on what might have happened to Lieselotte Schlenger. No witnesses, no suspects, no signs of suspicious activity (except for the fact that she’d been strangled to death with a piece of wire, of course). But on a bright teacup near Schlenger, the police found DNA, the only clue to surface at all.

The case went cold, given that the only lead was the DNA of an unknown woman, and there was no match. Yet.

Eight years later, in 2001, there was a match when the same woman’s DNA was found at a murder scene of a strangulation victim in Freiburg, Germany. Police now knew that they were dealing with a serial killer.

But this time, the woman didn’t wait another eight years to strike again.

Five months after the second murder scene, her DNA showed up on a discarded heroin syringe, after a 7-year-old had stepped on it in a playground in Gerolstein. A few weeks later it showed up on an abandoned cookie in a burgled caravan near Bad Kreuznach, like she’d deliberately spat out a Jammy Dodger as a calling card. It was found in a break-in in an office in Dietzenbach, in an abandoned stolen car in Heilbronn, and on two beer bottles and a glass of wine in a burgled bar in Karlsruhe, like she’d robbed the place but stuck around for a few cheeky pints.

And her activities were not confined to Germany.

Over the apparent crime spree, her DNA was sprayed across an impressive 40 crime scenes in Austria, southern Germany, and France, including robberies, armed robberies, and murders.

In 2009, the case took an even more bizarre turn.

Police in France had discovered the burned body of a man, believed to be from an asylum seeker who went missing in 2002. During his application, the man had submitted fingerprints, which the police used to try and confirm his identity. Only, once again, they found the DNA of the phantom.

“Obviously that was impossible, as the asylum seeker was a man and the Phantom’s DNA belonged to a woman,” a spokesperson for the Saarbrücken public prosecutor’s office told Spiegel Online in 2009.

But how could this be?

DNA evidence had tied the woman, or man, or whatever, to six murders and numerous other crimes. There was plenty of evidence to identify the criminal.

What went wrong?

Well, in 2009 police finally figured out how DNA evidence had ended up at all of these crime scenes in three countries.

The man’s death led to an explanation of the case: there was no serial killer, and the DNA could be traced to a woman working in a packing center specializing in medical supplies. It was all down to DNA contamination.

Well, couldn’t that packing woman be convicted of the serial murders and other crimes, based upon the DNA evidence?

No, because there was no other evidence linking the woman to the crimes, and certainly “reasonable doubt” (or the European criminal justice equivalent) that the woman was also the dead male asylum seeker.

This is why DNA is only an investigative lead, and not evidence in and of itself.

But the Innocence Project always believes that DNA is authoritative evidence, right?

Even those who champion the use of DNA admit this.

If you look through the files of people exonerated by the Innocence Project, you find a common thread in many of them.

Much of the evidence gathered before the suspect’s original conviction indicated that the suspect was NOT the person who committed the crime. Maybe the family members testified that the suspect was at home the entire time and couldn’t have committed the crime in question. Or maybe the suspect was in another city.

However, some piece of evidence was so powerful that the person was convicted anyway. Perhaps it was eyewitness testimony, or perhaps something else, but in the end the suspect was convicted.

Eventually the Innocence Project got involved, and subsequent DNA testing indicated that the suspect was NOT the person who committed the crime.

This in and of itself didn’t PROVE that the person was innocent, but the DNA test aligned with much of the other evidence that had previously been collected. It was enough to cast a reasonable doubt on the conviction, allowing the improperly convicted suspect to go free.

But there are some cases in which the Innocence Project says that even DNA evidence is not to be trusted.

Negligence in the Baltimore Police Department’s crime lab tainted DNA analysis in an unknown number of criminal cases for seven years and raises serious questions about other forensic work in the lab, the Innocence Project said today in a formal allegation that the state is legally required to investigate.

DNA contamination, the same thing that caused the issues in Europe, also caused issues in Baltimore.

And there may be other explanations for how a person’s DNA ended up at a crime scene. Perhaps a police officer was careless and left his or her DNA at a crime scene. Perhaps someone was at a crime scene and left DNA evidence, even though that person had nothing to do with the crime.

In short, a high probability DNA match, in and of itself, proves nothing.

Investigative leads and reasonable doubt are very important considerations, even if they don’t fit into a one-hour TV show script.

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