CRIME SCENE DNA DOES NOT EQUAL GUILT

Catching the Bad Guys Matters

Gathering evidence to catch violent criminals is a vital function of police. Believe it or not, even criminal defense attorneys want police to be able to catch violent criminals. After all, criminal defense attorneys live in the same jurisdictions as everyone else and have loved ones who could be at risk.

As a society, few things are more important to us than getting the bad guy and punishing him. It not only removes a dangerous person from society, it provides us with a sense of order and safety, among other claimed effects.

We Have Extreme Faith in Scientific Evidence Like DNA

However, and this is a HUGE however, caution is critical when using science to convict people of crimes. We rely upon science in life and death matters in countless ways every day, and our reliance is rapidly growing. People may sincerely claim religious faith can solve their problems, but when a scientific solution is available to solve their problems, people’s faith in science is almost universally applied.

Our faith in science can be misapplied, though, when we take an amazingly accurate scientific discipline and consider it a sort of talisman, an ultimate answer to our most pressing questions. Such a danger exists with the M-Vac DNA vacuum device described in the following article: http://www.ksl.com/?nid=148&sid=34568551  CSI may not be real, but the public can relate to this kind of device.

The availability of a machine able to capture invisible or dust-like particles of DNA by applying a vacuum to pieces of evidence and crime scenes is a remarkable development for law enforcement. Labs are capable of amplifying such dust-like DNA to identify DNA markers. Applied science is able to do some amazing things.

The DNA vacuum described in the article sounds terrific because it can pick up DNA where none could previously be extracted. Using a swab to collect DNA has a particularly frustrating limitation, including identifying where you should swab and what you should swab; you need to have an idea where DNA is or might be. Many times, no meaningful DNA will be found at a crime scene, and the M-Vac promises to find more than was previously possible. That’s great news, right? It might be. It could be great in some ways, but we must be careful to keep its application in perspective.

Your DNA Could be Found at a Crime Scene

Suppose for the moment YOUR DNA is found on a murder victim’s shirt by using the police vacuum, so the police identify you as the only suspect. Does your DNA on the victim’s shirt mean you killed the victim? Does it mean you were ever at the murder scene? Does it mean you ever met the victim? The answer to each question is NO.

What it means, IF the DNA testing were properly conducted, is a few of your cells were on the victim’s shirt, and nothing more, in and of itself.  Crime scene DNA does NOT equal guilt.

Most people consider DNA to be conclusive of guilt or involvement, and there is good reason for reliance upon DNA evidence. However, DNA evidence must be viewed in its proper context.

How Your DNA Got There May Surprise You

The problem with the evidence gathered by the M-Vac is it will often gather “touch DNA”. Touch DNA from YOU can wind up at a crime scene, even if you’ve never been there and never touched the item in question. Touch DNA can be practically everywhere. We leave traces of our cells on whatever we touch.

Imagine bumping into a guy in a public place, perhaps an airport, and your arm brushes against his shirt. Your DNA could wind up “discovered” on his clothes by the M-Vac after he’s been murdered.

You and a friend could also exchange touch DNA with a handshake, and each of you could further transfer each other’s touch DNA to each other person or thing both of you touch. Each person or thing we touch could then be transferred to anything or anyone coming into contact with them. Our DNA could literally travel to places we’ve never been and wind up on things we’ve never touched and on people we’ve never met.

Touch DNA no more conclusively proves a crime than dust blowing around town.

Touch DNA Holds Promise as a Crime-Fighting Tool, BUT…

In its proper place, touch DNA could be a good investigative tool for police, which may lead to catching the killer in the hypothetical proposed.

Further suppose they come to interview you after they identify the murder scene DNA as yours. They could follow up with you, only to discover you were 1,000 miles from the crime scene at the time of the murder. Even if you have been at the scene of a crime and left touch DNA, the question of when you were at the crime scene is not answered by DNA.

Just in case you are skeptical about touch DNA being easily transferrable, it has already caused at least one person to be falsely accused of murder.  An innocent man’s DNA was found on a murder victim’s body solely because paramedics used an oxygen monitor on his finger before applying the same monitor to the murder victim’s finger. See this link:http://www.mercurynews.com/crime-courts/ci_26055401/san-jose-case-casts-doubts-dna-evidence.

Contamination is a constant problem with evidence, and touch DNA presents a profoundly complex contamination risk. http://www.forensicmag.com/articles/2013/04/touch-dna-crime-scene-crime-laboratory

Police will still have a potentially useful tool with the DNA vacuum because they may gain leads to follow in their unsolved case. They might even get lucky enough to find the killer or develop other leads they could not have known existed without the touch DNA.

Rather than jumping to conclusions and condemning people accused of crime because of the supposed conclusiveness of DNA “evidence”, we owe it to ourselves as a society to step back and view evidence from a reasonable perspective.

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