DNA Tests Highlight Problems with Many Forensic Tests

Some forensic tests are flawed due to their lack of scientific rigor, while others are susceptible to human errors and mistakes, and technology may not improve this situation

People love technology. Police love technology. Courts love technology. Technology seems to provide both convenience and certainty. How tall is Mount Everest? How long is the Great Wall of China? Virtually any question can now be quickly answered with the smartphone you carry in your pocket or purse.

Wouldn’t it be great if we could produce the same certainty with criminal justice? Police could, CSI-like, run a test or scan a crime scene and immediately produce the guilty party? Unfortunately, the real world does not work like that. Few tests provide the 100 percent certainty we all would like.

The promise of DNA tests

However, DNA comes close. The technique of examining evidence at a crime scene, like blood, saliva or skin, and using it to positively identify a victim or a perpetrator can be very accurate. Analyzing elements of human genetic structure, it can provide probabilities of a match that seem to provide scientific certainty in the uncertain world of the criminal justice system.

However, like every other piece of physical evidence used in a criminal trial, it is subject to one serious caution. The test is only as good as the process itself. If the investigators collecting the blood are sloppy, it the technician testing the sample is lazy, incompetent or too eager to please the police or prosecutor, the results may be irrevocably corrupted.

Crime labs across the nation have been rocked by scandals, ranging from gross incompetence to technicians intentionally faking tests to increase their production. Often, there is an inherent conflict of interest, with the lab being funded by and operated as a division within the police department, county sheriffs’ office or other law enforcement arm of the state.

Some labs even receive financial compensation for producing “right” answers that allow prosecutors to obtain convictions.

Some have suggested that the creation of computerized analysis of DNA would solve the issue of poorly trained, overworked or misguided crime lab employees. This simply steps the question one more layer back in the process. We would then have to ask how competent is the computer test and how was its software written?

A double-edged sword

DNA evidence, when handled properly, can be highly accurate and has been used in numerous exonerations, demonstrating that persons convicted of crimes decades ago did not commit them. But that does not excuse the potential for misuse.

Worryingly, with more sensitive tests becoming available, the potential for misidentification of those accused and wrongful prosecutions may be greater than ever. In one incident from 2012, police arrested a homeless man and charged him with murder, as investigators found DNA from the victim under his fingernails.

It turned out, he had been assisted by paramedics the same night as the murder, and those paramedics had been at the murder scene prior to treating the homeless man. Only the discovery of hospital records confirming that he was in detox at the time of the murder prevented his prosecution and likely conviction.

DNA evidence can be contaminated from numerous sources, including such seemingly innocent activities as shaking hands. The danger in being able to detect minuscule amounts of DNA is that DNA is revered so highly that when dealing with a case that has no clear perpetrators, a shred of DNA may cause police to focus their investigation on the wrong person.

The burden of the State in a criminal prosecution is guilt beyond reasonable doubt. Forensic evidence is often touted as a means of eliminating reasonable doubt. Prosecutors want convictions and DNA and other tests often seem to provide the “magic” evidence that ensures they win another conviction. Nevertheless, such evidence needs to be “proven” to be what it claims to be, not simply what prosecutors wish it to be.

The trouble with forensic evidence

Crime lab scandals throughout the country are only one tip of the iceberg of problems that beset the criminal justice system. Even a state like Minnesota, which is generally regarded as having professional crime labs, experienced the six-month shutdown of the St. Paul crime lab after examples of slip-shod work and errors came to light.

Many so-called scientific tests are bogus, lacking any scientific rigor. One examination of FBI microscopic-hair sample matches found errors in 90 percent of comparisons. This from the FBI, the nation’s preeminent law enforcement organization. Imagine the potential for error from many of the far-less-well-funded crime labs that process evidence at the state level?

Bite-mark analysis has been so discredited that the Texas Forensic Science Commission has recommended it being banned from use in criminal trials. Other forensic “evidence,” such as that used in some arson investigations has also been labeled “junk science.”

It is not known how many innocent individuals have been sentenced to prison or death on faulty evidence, but the known cases are too numerous to ignore. A large part of the problem is due to the unreserved acceptance by many courts of this junk science.

In a 2011 U.S. Supreme Court case, Bullcoming, the Court ruled that lab technicians have to be available, even if a test is thought to be “reliable” to satisfy the Sixth Amendment’s confrontation clause. Given the questionable “reliability” of many forensic tests, this type of confrontation seems all the more important in every case in which testimony by an expert regarding a test is produced.


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