Forensic Science

Evidence Collection

Some real evidence cannot be moved from the scene, so photographs and sketches must be detailed enough to accurately represent the scene both to new parties, such as a jury, and to investigators who need to refresh their memories about a scene's details. Latent prints should be developed at the scene when the surface on which they are found cannot be transported. After careful photographing, the prints can be lifted and transferred to fingerprint cards.

Chain of custody must be maintained for each item of evidence, with a log created and kept of each person in whose possession the item has been. Chain of custody logs are increasingly maintained via computer software, utilizing a unique bar code for each item.

Evidence that can be collected to be processed at a lab should be. Packaging options vary greatly depending on what evidence needs to be preserved. For instance, arson evidence is best packaged in clean, empty paint cans because they seal tightly enough to preserve accelerant vapors.

Conversely, blood swabs, wet items, and anything that might contain DNA should be packaged in paper or cardboard rather than plastic, metal, or glass, as the breathability of paper-based materials will prevent fungal or bacterial growth that could damage/destroy evidence. Large, wet items (such as blood-stained clothing) should be dried in a drying locker before storage to prevent spoilage.

All items should be labeled with the location found and description, then sealed with the finder's initials and the date written across the seal and overlapping onto the package exterior.

Unless expressly credited, all images copyright Kylie Kells Dickson, 2022.


References

Donley, R. M. (2018a). Criminal Evidence. Pearson.

Hall, D. E. (2015). Criminal Law and Procedure. Cengage Learning.