A vehicular homicide trial in Fayette County, Georgia featured DNA expert witness testimony focused on determining whether or not the Defendant was behind the wheel at the time of a fatal one-car accident. Serene Richter, 46, stands accused of causing the accident while under the influence of alcohol, but has disputed the prosecution’s ability to prove that she was driving the car and caused the crash that killed Samuel McKnight, 44.

Driver Uncertain in Vehicular Homicide Trial

On June 6^th, 2011 a Hummer H3 carrying both Richter and McKnight careened off Bute Road in North Union, Georgia, rolled several times, and killed the 44-year-old McKnight after striking a telephone poll. After investigation into the accident, police charged Richter with homicide by vehicle, homicide by vehicle while driving under the influence, driving under the influence, and several traffic violations. Prosecutors claim that Richter was driving with a blood alcohol level of 0.142 at the time of the accident, making her guilty of all charges.

Richter’s attorney, in response, contends that it was Samuel McKnight, whose blood alcohol level was 0.255, who was driving the car and Richter was the passenger. In an effort to settle the dispute over which occupant was behind the wheel of the vehicle, two forensic expert witnesses were called to discuss DNA evidence on the driver’s side airbag that could identify who caused the accident.

Vehicle Manslaughter Case Uses DNA Expert Witnesses

Amy Irwin, a forensic DNA expert witness from the police crime lab, took the stand to explain that she and another scientists studied DNA profiles of samples taken from the driver’s and passenger’s side airbags of the H3. According to Irwin, the passenger airbag did not provide sufficient DNA to identify either Richter or McKnight as the passenger, but aided prosecutors by testifying that there was substantial DNA on the driver’s side but none of it belonged to McKnight – indicating that he had not been driving at the time of the accident.

Sara Harner, another DNA expert witness working as a police forensic scientist, supported Irwin’s findings by testifying that Richter’s DNA was on the driver’s side airbag but not on the passenger side. Both expert witnesses withstood rigorous questioning from Richter’s attorneys regarding the reliability of the DNA evidence due to the fact that the samples were not collected from the vehicle until a week after the crash, and spent more than two years in storage before laboratory testing.  Harner, however, told the court that the DNA was properly stored and untainted.

DNA Expert Testimony Tells Partial Story

While the testimony by DNA expert witnesses Irwin and Harner bolster the prosecution’s argument by indicating that Richter was on the driver’s side while McKnight was not, both forensic experts acknowledged that the DNA did not definitively align the occupants. Attorneys for Richter concluded the cross examination by inquiring whether or not it was reasonable that the placement of DNA was the result of unrestrained occupants shifting places while the vehicle rolled, and the experts had to concede that possibility.

Although DNA results carry gravitas as convincing physical evidence, the Richter trial demonstrates that it cannot make an open-and-shut case, particularly in a criminal trial where prosecutors must convince jurors of guilt beyond a reasonable doubt. Whenever DNA traces are left behind, attorneys must investigate the circumstances of the incident to piece together the puzzle explaining exactly how and why the DNA was present at the scene. Given the weight attached to DNA, attorneys opposing the evidence must be prepared to question forensic experts in such a manner that casts doubt on the strength and integrity of the evidence. Whether or not Richter’s attorney poked sufficient holes in the prosecution’s DNA expert testimony by casting doubt on the evidence’s ability to affirmatively place the defendant behind the wheel remains to be seen as the trial is expected to go to jury in the coming weeks.