Exhibit A Season 1 Episode 4 Touch DNA

Exhibit A is a true crime documentary series focusing on the science and technology used to help solve criminal cases. Season 1, episode 4 titled "Touch DNA" explores how forensic analysis of DNA found on objects can help solve crimes.

The episode begins with the case of a woman who was brutally murdered in her own home. Despite there being no physical evidence or witnesses, the police were able to solve the case through the analysis of DNA found on a doorknob. The DNA belonged to a man who was known to the victim but had no connection to the crime scene. Through further investigation, it was revealed that the man had visited the victim's home just hours before the murder. He was subsequently charged and convicted of the crime.

The episode then delves into the science behind DNA analysis and how it has evolved over the years. The traditional method of DNA analysis involves extracting DNA from blood, semen, or saliva found at the crime scene. However, a newer technique called touch DNA analysis has revolutionized the field. Touch DNA refers to the microscopic amount of DNA left behind when someone touches an object. This can include skin cells, hair follicles, and sweat.

The episode features experts who explain how touch DNA analysis works. They collect samples from various surfaces and demonstrate how even a small amount of DNA can reveal a lot about a person. Touch DNA analysis has the potential to identify suspects who may have touched an object even if they were not present at the crime scene. It also has the potential to solve cold cases where DNA evidence was found but could not be linked to a suspect.

The episode then moves on to another case where touch DNA analysis played a crucial role in solving the crime. A woman was found raped and murdered in her own home, and the police had no leads or suspects. Four years later, a man was arrested for an unrelated crime, and his DNA was found to match the DNA found at the crime scene. Through touch DNA analysis, the police were able to show that he had been inside the victim's home. He was subsequently charged and convicted of the crime.

The episode also explores the limitations of touch DNA analysis. It can only detect human DNA, so if the perpetrator wore gloves or used a weapon, the analysis may not be useful. It can also be contaminated easily, which can lead to false results if the sample is mishandled.

The episode concludes with the case of a man who was wrongfully convicted of a rape that he did not commit. The victim had identified the man in a lineup, and DNA evidence found on her clothing appeared to match his. However, when touch DNA analysis was conducted on the clothing, it was found that the sample was contaminated. The man was subsequently exonerated, and the real perpetrator was later identified through DNA found on a different victim.

Overall, the episode highlights the importance of touch DNA analysis in helping to solve crimes. It also emphasizes the need for careful handling of DNA samples to avoid contamination and false results. The episode provides an informative and engaging look into the technology used in modern crime fighting.