Touch DNA Analysis: Advantages, Limitations, and Best Practices

Introduction

Touch DNA analysis, the process of obtaining DNA profiles from skin cells left behind on crime scene items, has revolutionized forensic investigations. This emerging biometric tool allows investigators to link suspects to crime scenes through trace amounts of DNA. Touch DNA analysis has become a powerful tool in forensic investigations, aiding officers in linking suspects to crime scenes. However, it is essential to understand its limitations and challenges to ensure its appropriate use. In this comprehensive article, we delve into the world of touch DNA, exploring its advantages, obstacles, and best practices for successful DNA evidence collection and analysis.

Advantages of Touch DNA Analysis

1. Linking Suspects to Crime Scenes: One of the significant advantages of touch DNA analysis is its ability to establish connections between suspects and crime scenes. Trace amounts of DNA left behind by touching items can be instrumental in identifying potential perpetrators, helping law enforcement agencies build strong cases against criminals.
2. Forensic Evidence for Property Crimes: Touch DNA analysis serves as a valuable forensic tool, particularly in property crime investigations. When suspects leave behind skin cells on items at the crime scene, investigators can use touch DNA analysis to collect crucial evidence that links them to the scene of the crime.
3. Non-Invasive Collection: Unlike other DNA collection methods, touch DNA analysis is non-invasive, making it a convenient and less intrusive way to obtain DNA samples. It reduces the need for invasive procedures, thereby easing the process for both law enforcement and potential suspects.
4. Potential in Cold Cases: Touch DNA analysis has opened new possibilities for solving cold cases. Even years after a crime has occurred, trace amounts of DNA left behind on items can be analyzed, providing fresh leads and renewing investigations.

Limitations of Touch DNA Analysis

1. Sufficient Skin Cell Quantity: To generate a usable DNA profile, a suspect must have left behind enough skin cells on an item. Factors like the duration of contact and the frequency of touching play a crucial role in obtaining sufficient DNA for analysis.
2. Item Suitability: Not all items are suitable for touch DNA analysis. Items that have not been in contact with the skin for an extended period may yield insufficient DNA, making it challenging to obtain a conclusive DNA profile.
3. Mixture Profiles: Touch DNA analysis may fail for items used by multiple individuals. In such cases, the DNA obtained might be a mixture of DNA from different people, making it difficult to attribute the DNA to a specific suspect.
4. Degradation over Time: Touch DNA left on items can degrade over time due to environmental factors like exposure to sunlight, moisture, and extreme temperatures. This can hinder the successful extraction of usable DNA from the item.

Best Practices for Touch DNA Collection

1. Preferred Order of Collection: When investigating crime scenes for DNA, it is crucial to follow the “best evidence” order of collection. Blood samples should be collected first, followed by items with saliva contact, and touch DNA items should be considered as the last resort.
2. Suitable Touch DNA Examples: Clothing, hats, sunglasses, steering wheels, and tools brought by suspects are examples of suitable items for touch DNA analysis. These items are more likely to yield sufficient DNA for analysis.
3. Unsuitable Touch DNA Examples: Items like fingerprints (smudges or partials), thrown objects, public items (doorknobs), ammunition, and wrappers are not suitable for touch DNA analysis. Attempting to collect DNA from such items may lead to inconclusive results.
4. Selective Submission of Evidence: Submit only the best evidence items to the DNA lab to produce quality DNA profiles. Quality over quantity is essential to reduce the backlog of poor quality evidence and prioritize cases with substantial DNA evidence.

Conclusion

Touch DNA analysis has proven to be a valuable tool in modern forensic investigations. Its ability to link suspects to crime scenes through trace amounts of DNA has helped solve numerous cases. However, it is essential to acknowledge the limitations of touch DNA analysis and follow best practices during evidence collection. By doing so, investigators can maximize the potential of touch DNA analysis, leading to more successful case resolutions and ensuring justice for victims.