Introduction: There will be times the crime scene investigator or evidence recovery technician will be given the task of collecting suspected tire standards for comparison or elimination of tire track impressions that were recovered at a particular crime scene. There are many products on the market designed to accomplish these task. But what does the investigator do if his/her agency or department doesn’t have the commercial products on hand. This article is written to assist by allowing the investigator to use a few items that are easily available to him/her in retrieving the suspected standards at minimal cost. Being flexible and adaptable are very important. The investigator will only be limited to his or her imagination.
Items needed for the task:
- one 13 oz. jar of pure petroleum jelly (Vaseline).
- black fingerprint powder
- one cardboard box
- white or yellow grease marking pencil
- sharpie permanent marking pen
- pair of latex gloves
- utility knife
This 2 step process will make recovering suspect tire standards very simple.
A cardboard box or foam board is recommended since the investigator is not always going to have a smooth flat surface to work from. The cardboard or foam board will allow the investigator to retrieve the suspected standard from the tire without all of the background noise from the surface appearing in the recovery medium. The average tire width of most vehicles will vary in tread pattern size from 6 to 8 inches in width. Take the cardboard box and cut it into working strips approximately 18 inches to 24 inches wide using the length of the entire box. It is preferred to make the strips wider than the tread pattern size of the tire so that the investigator has an area to mark along the side of each collected strip with the information needed. Since you will need to retrieve the entire circumference of the tire 3 to 4 strips may be needed for each individual suspect tire standard.
Take a jar of Vaseline. Scoop out 3 to 4 large table spoons full of Vaseline from the jar. Replace the Vaseline that was removed from the jar with 3 to 4 table spoons of black fingerprint powder. Mix the formula together in the jar. Make sure you are wearing a pair of latex gloves, since this process tends to be on the messy side.
To best replicate conditions of the suspect tire, the tire standard should be taken while the tire remains mounted on the vehicle. Scoop out a generous portion of the mixture with the gloved hand and begin applying it to the tire. Work the mixture over the exposed portion of the tire. The key is to apply an even thin coat of the mixture onto the tire surface.
As you have probably figured out at this point this is not a task for the lone ranger and will require assistance to accomplish. With the permanent marker, label the first strip with the appropriate information and line it up on the surface against the tire. Use the marking pencil to establish and mark on the tire the starting rotation point. Slowly roll the vehicle allowing the tire tread pattern to transfer to the strip. Place your second strip on the surface against the first strip allowing the uninterrupted pattern to continue. At this point stop the procedure long enough to apply a thin even coat of the transfer mixture onto the uncoated portion of the tire. Now continue the sequence until the rotation (marked area of tire) is completed. Lay the strips aside and allow the transfer mixture to dry. Do not stack the strips during the drying stage.
For drying and transport the investigator can opt to take a large empty box. Cut angled slots along two sides of the length of the box. This will allow the investigator to stand the recovered strips without their touching.
Suggested information to be placed on the individual recovered strips:
- Police or Agency designated case number.
- Investigator’s initials and identification number.
- Tire manufacturer.
- Tire size.
- Tire Serial Number.
- Alpha-Numerical strip indicator.
- Tire placement.
There are many items that can be used for this technique, i.e.; paste shoe polish, latent fingerprint ink, etc. Try a couple of test strips and check with the laboratory that will do your comparisons to ensure that this method meets their standards. Remember that safety in any task is the first responsibility.