DNA makes way for mRNA in forensics

(PhysOrg.com) -- The use of DNA testing to identify a criminal or victim is now commonplace in crime scene investigations. However, DNA has its limits, as it cannot date a stain of bodily fluid to help investigators determine when a crime was committed. But messenger ribonucleic acid (mRNA) can.

“Bodily fluids are the most common elements of proof on crime scenes,” says Anne-Marie Simard, a biochemistry master’s student at the Université de Montréal. “Imagine a couple who is separated. Three months later, the woman is sexually assaulted in the living room of what was the couple’s house. In the crime scene analysis we discover her ex-husband’s sperm on the living room couch. Did the stain exist before the crime was committed? mRNA can answer that question.”

Messenger RNA is a temporary copy of DNA used in the synthesis of proteins. Once it accomplishes its task it begins deteriorating. “Depending on the type of mRNA it can last anywhere from several hours to several weeks, contrarily to DNA that remains intact,” says Simard.

Simard used the laboratories at the Sureté du Québec offices where she manipulated various samples of blood, saliva and sperm. For each of the fluids Simard studied the degradation of four mRNA molecules over a six-month period. Some samples were kept at room temperature while others were frozen at -80 degrees Celsius.

“I wanted to see if freezing the samples stopped the deterioration,” says Simard. “Because samples are not always analyzed immediately. They are often frozen which is why it’s important to understand if the mRNA remains intact despite the temperature change.”

The use of mRNA in police investigations is a delicate endeavor. The instability of the molecule requires strict manipulation in laboratories. “It will be many years before mRNA testing can be used in a court of law,” says Simard. “I just hope my research is a step in that direction.”

Provided by University of Montreal