Popular crime shows would have you believe that the analysis of forensic evidence is the key to finding the perpetrator of a crime. But is forensic evidence reliable?  DNA evidence, blood spatter patterns, bite marks, finger prints and other common types of forensic evidence have been subjected to scrutiny and some just don’t hold up. For example, I previously wroteabout an innocent man who spent 33 years in prison based on bite mark analysis – a forensic evidence technique that has been discredited in the scientific community but continues to be used by prosecutors.

Similarly, other forensic analysis methods have been questioned, or even debunked, by science but continue to be an important part of the prosecution’s arsenal. In the popular imagination, these techniques provide a slam-dunk conviction. But most members of the public, from whom a jury of peers is selected, would be surprised to learn—and perhaps even reject—the proposition that quite often forensic evidence is nothing but junk science. Overcoming this bias takes the persuasive skills of criminal defense attorney who is up on the science and can communicate a reasonable doubt about the forensic evidence.

Here’s one that may surprise the average reader: Even positive DNA evidence may not be evidence at all. The common assumption is that if a suspect’s DNA is found on the victim or at a crime scene, the suspect is positively implicated in the crime. But that is not always true. Often the DNA evidence is in trace amounts but is thought to be conclusive evidence of the suspect’s presence at the scene. DNA analysis has become so sophisticated that forensic technologists can pick up even the smallest amounts of DNA. The problem is that humans shed DNA all the time and everywhere. When you touch anything, you will leave your DNA. Another person touching the same object can then pick up your DNA. This is referred to as the “touch-transfer” property of DNA. So, imagine that you took a public bus. Another passenger on that bus picked up your DNA and shortly thereafter committed a crime. Your DNA may very well show up in forensic analysis, implicating you in the crime.

Another common forensic analysis technique is what is called “blood-stain pattern analysis.” It is widely used in courtrooms across the country and has been key evidence in the conviction of many, some of whom were later exonerated. The technique involves examining the patterns of blood spatters at a crime scene to recreate how the crime was carried out. Although it continues to be used by the prosecution to this day, it is widely questioned as having no scientific reliability at all.

How, you might wonder, does our justice system continue to allow this evidence in and even rely on it for a conviction when the scientific validity is questionable? That is a complicated question not easily answered. Part of the answer though lies in the court precedent. When an appellate court lets this evidence remain after being challenged as unreliable or otherwise inadmissible, the ball starts rolling. One appellate court after another will defer to preceding decisions.

Another problematic area is that labs, law enforcement, and even the prosecutioncan manipulate the forensic evidence from outright fabrication, to omission, to misleading testimony and many other unscrupulous methods for securing a conviction. Often it takes an alert criminal defense attorney to convincingly point out the errors in the forensic evidence.

Most jurors believe forensic evidence is science; unfortunately, it often is not. Orange County criminal defense attorney William Weinberg has 25 years’ experience defending those accused of crimes all the way to trial. He stays on top of the latest science regarding forensic evidence and scrutinizes that evidence every step of the way. Attacking the evidence is often crucial to the outcome of the case. If you have been charged with a crime, contactAttorney Weinberg at 949-474-8008 or by email at bill@williamweinberg.comfor a free consultation regarding your matter and a review of the evidence presented by the prosecution.