Think DNA Evidence Can't Possibly Be Wrong? Think Again

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Most people alive today hardly remember a time when DNA evidence wasn't permissible in court. The genetic material that humans shed in every skin cell or drop of blood has become so important to criminal proceedings that prosecutors sometimes despair of proving a case without it. That's been especially true since the rising popularity of "crime shows" started familiarizing the general public with accounts of biological evidence used to solve various murder mysteries.

That's led a lot of people to think that DNA evidence is always accurate, always irrefutable. However, that's far from the truth. Here's what you should know.

DNA Has a Controversial Place in the Courtroom

Despite scientific awareness of DNA evidence, it didn't start to be accepted as valid in courtrooms until the 1980s. Its use was first upheld in a state court in 1988. Since then, however, it's become a regular part of the criminal justice system's array of tools against defendants.

DNA evidence is not without its detractors, however. While prosecutors like to present DNA evidence as infallible, defense attorneys say that doing so is irresponsible and a disservice to justice. They point to issues with improper collection procedures, bad lab work, and faulty mathematics, among other things, that should erode a jury's confidence in the evidence. 

Mistakes Show the Fallible Nature of DNA Evidence

There have been some big mistakes involving DNA evidence that have galvanized the ongoing dispute about exactly how it should be used in a courtroom. They mostly illustrate how easy it is to get the wrong conclusions despite the use of good science.

For example, a 26-year-old homeless man was nearly convicted of the murder of an elderly Silicon Valley executive in a home invasion--despite the fact that he was in a hospital miles away at the time. His DNA was allegedly found under the victim's fingernails. A phenomenon known as "secondary transfer" was eventually found to be at fault.

Essentially, DNA from the homeless man was left in the ambulance he'd ridden to the hospital in earlier that night. It then transferred to the paramedic who examined the murder victim's body and, eventually, to the murder victim's hands.

Similarly, the same phenomenon was responsible for sending German authorities on a wild goose chase for a phantom they thought was behind around 40 different crimes. It turns out that they didn't have a serial killer on their hands--just cotton swabs that had all been accidentally contaminated during their manufacturing process by the same woman. Police have wasted more than ten years looking in the wrong direction due to DNA.

Defendants and Jurors Should Be Skeptical

Whether you're the defendant in a case involving DNA evidence or sitting on the jury, you should be skeptical of DNA's reputation as an absolute authority. The absence of DNA evidence may be useful as a tool to exclude someone from guilt in a crime--but its presence doesn't mean that a case is clear-cut.

An experienced criminal defense attorney can--and should--demonstrate exactly why DNA evidence shouldn't be relied on all the time. Ensure that you only hire criminal defense attorneys that can offer more then just DNA evidence. Look to a local firm like The Fitzpatrick Law Firm if you need an attorney now.