12 detective tips


1. Use a new, clean fingerprint brush for each crime scene to prevent cross contamination of DNA.

2. Never place items containing DNA evidence into plastic bags. Plastic retains moisture, which can degrade or damage DNA.

3. When collecting potential DNA evidence (blood, urine, saliva, semen, etc.) from an object—walls, baseboards, bed posts, car windows, steering wheels, light switch covers, refrigerator door handles, etc.—use a clean, fresh swab. First, though, moisten the swab with sterile distilled water. Once the sample is collected onto the swab, place it inside a cardboard or paper container for air drying. ALWAYS use a fresh cardboard and/or paper container to prevent cross contamination.

4. Use adhesive side powder for lifting prints from the sticky side of tapes, packing labels, etc. Mix the side powder with water and dispersing agent until it reaches the consistency of thin paint, then apply it to the surface. Wait 10-15 seconds and then rinse with clean water. Presto! The print(s) appear instantly.

5. Polyethylene tape is great for lifting prints from curved surfaces. The material easily conforms to the shape of non-flat surfaces, such as a doorknob.

6. To prevent contamination, do not talk, yawn, cough, sneeze, etc. over potential DNA evidence.

7. When seizing computers as evidence – If the device is on, do not use it. Photograph the image on the monitor and then unplug the power cord from the machine (remove the battery from a laptop). If the computer is not on, do not power it up. Deliver the devices to the crime lab for examination by computer experts.

8. Use SPR or Wet Print to lift prints from wet surfaces. By the way, both products are water-based, which means they cannot be used when temperatures are below freezing.

9. Do not store or transport potential DNA evidence in direct sunlight, or in areas exposed to excessive heat (vehicle dashboard, trunk, etc.).

10. Typically, embalmed bodies are not suitable for DNA testing. However, it is possible to obtain DNA from bone and hair, even on a body that has been embalmed.

11. A “how-to” kit is available to law enforcement that details (step-by-step) the process of collecting insect evidence. The kit also contains a list of entomologists who’ll help identify the bugs and their stages of life.

12. Every single item found at a crime scene should be considered as evidence until it’s ruled as having no evidential value. For example, broken window glass should be recovered as evidence. It may be possible to match the glass to particles discovered embedded in the soles of a suspect’s shoe. Likewise, hairs, fibers, soil, and other trace evidence may be found on a suspect’s clothing and shoes.

I once matched a particular soil/plant mixture found on the brake pedal of a suspect’s car to that of an area where the combination of the two was specific to a very small region…the precise place where the victim was killed.

*Crime-solving is akin to working a jigsaw puzzle. And we all know individual puzzle pieces rarely make sense on their own. It’s when all the pieces are connected that we see the big picture. For now, though, when using the analogy of comparing a murder to a jigsaw puzzle, let’s substitute “puzzle pieces” with bits of crime-scene evidence.

As the detective locates, aligns, and joins each section to another, it’s not long before the assembled pieces form one large image with the suspect as the centerpiece. However, if the officer leaves too many pieces behind, well, the puzzle remains incomplete. Therefore, it’s likely the killer will go unpunished for his crime. It’s also possible he’ll murder again…and again, and again.