Trace DNA, also known as ‘touch’ DNA, has the power to make a match with as little as 7-8 skin cells. But how reliable is DNA evidence in its smallest amounts? Should we count on DNA alone to Convict for Murder Charges?
Our personal DNA is constantly being shed within our environments. Handshakes, hugs, holding the railing while walking down the stairs– these seemingly benign interactions can become the source of DNA cell transfer. From the Wired article Framed For Murder By His Own DNA “We leave a trail of ourselves everywhere we go. An average person may shed upward of 50 million skin cells a day… in two minutes the average person sheds enough skin cells to cover a football field. We also spew saliva, which is packed with DNA. If we stand still and talk for 30 seconds, our DNA may be found more than a yard away. With a forceful sneeze, it might land on a nearby wall.”
Criminal investigators search meticulously for DNA left at crime scenes– even in its smallest form. Since 1997, advances in DNA testing mean that even trace DNA samples can provide admissible evidence. And it isn’t just bodily fluids that can be used to detect DNA, but the mere touch of an object can transfer as little as 7-8 skin cells to create a relevant investigation profile. What once took a sample the size of a quarter can now be analyzed by a mere collection of cells taken off a door handle or nail shaving.
Forensic DNA testing can be used to not only identify a suspect but exonerate those wrongly accused. But these advances in trace DNA research come with warnings of a phenomenon known as “secondary transfer.” This is when a few small cells can appear on items a person has never touched. Secondary transfer can contaminate results and point the finger at almost anyone. But how?
ALCOHOL, ALIBI, ARREST
One such example occurred in December 2012. A homeless man was arrested on suspicion of the murder of a Silicon Valley millionaire. The victim was bound with duct tape during a home invasion and eventually suffocated. Trace amounts of Lukis Anderson’s DNA were found in the dead man’s fingernail clippings. While initially not connected to the crime, Anderson’s DNA (in the law enforcement database from former arrest) came up as a profile match. Anderson was arrested, charged, and faced murder charges and a possible sentence of life in prison if convicted.
But Anderson had an alibi. A reliable alibi. He had been ambulance transported to a nearby hospital where medical records showed inebriation to the point of near unconsciousness. Blood alcohol tests indicated he had consumed the equivalent of 21 beers, and he was admitted to the ER where he spent the night. The hospital and transport records gave his treatment time and date as precisely the time the victim’s home had been burglarized.
A FAMILIAR NAME
Mr. Anderson worked with his defense attorney to reconstruct his schedule on the day of the murder. His memory, though, was hazy. Eventually, a familiar name stuck out.
After he’d collapsed in the aisle of a local convenience store, Anderson was treated and transported by an EMT service. It was the same EMT service that checked the vitals of the victim at the scene of the murder. The pulse oximeter, which is used to measure how much oxygen is in the body, had been slipped over both patients’ fingers. It was determined to be the origin of the mixed DNA. Mr. Anderson was released after about six months and the charges against him were eventually dropped.
DNA USE IN THE CRIMINAL JUSTICE SYSTEM
DNA is generally used in the criminal justice system in two basic ways:
DNA is taken directly from a suspect and compared against a DNA sample found at the scene of a crime.
A DNA profile is run from a sample found at a crime scene against previously collected DNA profiles stored in a digital database to identify potential suspects who have not yet been identified.
Forensic investigators must be well trained in the collection and handling of biological samples. Care must be taken to minimize the risk of contamination and ensure that any samples removed from the scene of a crime are stored carefully. With secondary transfer, opening a cab door handle or pushing a grocery store cart could mean a stranger’s cells could transfer onto someone else’s hands.
Trace DNA has been criticized for high rates of false DNA “hits” sometimes due to this sort of contamination issue. According to The Marshall Project, “…Complex mixtures of many DNA profiles can be wrongly interpreted, certainty statistics are often wildly miscalculated, and DNA analysis robots have sometimes been stretched past the limits of their sensitivity.” If traces of DNA can make their way to crime scenes never visited, isn’t everyone a potential suspect?
Mr. Anderson’s case provides an example of a trace DNA transfer which implicated an innocent person. Reliance on DNA evidence, often treated as infallible, actually carries tremendous risks. A 2008 study found jurors believed DNA evidence as “95 percent accurate and 94 percent persuasive of a suspect’s guilt” (The Marshall Project). These false implications can have a disproportionate impact on minorities, who are often more searched, ticketed and arrested. A felony arrest is enough cause to collect a DNA sample which can be held indefinitely in law enforcement databases.
Like any piece of evidence, DNA should be viewed in the context of a bigger picture with some level of skepticism and restraint. Without more than DNA, a jury could have convicted an innocent man.
Should you find yourself charged with a crime, contact Columbus, Ohio defense lawyer, Joseph Edwards for a free consultation. Practicing for over 25 years, Attorney Edwards represents individuals at both the state and federal levels. Call today at 614-309-0243.