We’re starting to see a lot more criminal cases prosecuted, at least in part, due to evidence based on defendants’ alleged fleeting contact with an item or person. Known as “touch-transfer DNA” (or “touch DNA”), forensic investigators claim that this evidence can place defendants at crime scenes and link them to criminal activities.
But is it based on sound scientific principles? Or could it falsely implicate defendants due to its inherent limitations? Let’s delve deeper.
Limitations of the science?
The discovery of DNA profiling has been a game-changer in criminal investigations. But the pendulum may have swung too far in one direction with the reliance of touch DNA to solve crimes.
For one, it is impossible to prove when or how the traces of DNA were deposited. Some investigations have stalled when it was revealed that the alleged DNA depositors were dead or still small children.
Why it’s still junk science
When analyzing touch-transfer DNA samples, investigators deal with samples of fragmentary DNA. These cells typically are degraded, decaying and might have a mix of DNA from multiple people.
Under those circumstances, how can one defendant’s alleged DNA be isolated and proven to be connected to the crime?
Which cases rely most on touch DNA?
Often, its law enforcement supervising cold cases of homicide in the community who try to find perpetrators using touch-transfer DNA. Already grasping at straws to solve open homicides, the cold cases frequently have a dearth of evidence collected.
But investigators can falsely link people to crimes by relying on touch DNA samples’ veracity. According to research compiled by the Forensic Science International’s Genetic Supplement Series last decade, they found that there was an “increased chance of detecting the transfer of DNA from individuals not involved in [crimes] . . . to scenes and/or exhibits of the cross transfer of DNA between scenes or items.”
Craft a defense that attacks junk science
When your liberty is at stake, pull out all the stops by building a robust defense against shaky evidence like touch DNA.