Lab 2

One plastic dinking straw

One plastic tablecloth with rough surface or grainy surface ($1.00- Dollar General or Family Dollar)

One small model paintbrush or soft make-up brush

One small old ink toner cartridge from printer or copier

Scissors

Small sharp-pointed knife

One small bottle of Elmer’s Blue Gel-Glue (clear blue in color) available at Staples or Office Depot

Wide roll of clear Scotch tape

One sheet of white paper

One old coffee cup

Lab Directions:

This technique is called “Rough Lift.” It is very difficult to lift latent prints from grainy surfaces such as the dashboard or steering wheels of cars, oxidized exterior air conditioners, metal doors and many other surfaces. Using regular lifting tape will not sufficiently recover a latent print from the lower regions of a textured surface. Therefore, the following technique is an excellent way of recovering those difficult prints from textured surfaces.

This technique is to be employed after photographing the print in a field situation where this method is being used to produce an item of evidence; it is not necessary to photograph the print during this lab.

First, cut several six-inch squares from your textured plastic tablecloth.

Second, break open your old toner cartridge to recover the remaining bit of toner in the cartridge. Place the toner into your old coffee cup, and set it aside.

Next, take one of your squares that you cut from the rough plastic tablecloth, and place an oily (rub your forehead for adequate oil) thumb print in the middle of the tablecloth square.

Then, take your small paint or make-up brush and dip it into the toner in the bottom of your coffee cup. Make sure that all excess powder is off of the brush by lightly tapping the brush with your finger. Too much powder will cause a problem in developing your latent print.

Next, place your square of tablecloth on a flat solid surface, and brush lightly over your known fingerprint going in a circular motion. Continue working on the print until it is developed well enough to see clearly. This may take several attempts; this is why you cut several squares from the tablecloth.

Once the latent print is developed to your satisfaction, place a drip of Elmer’s Blue Gel-Glue, about the size of a dime, directly under your developed latent fingerprint; just touching the edge of your print. Using the plastic drinking straw, placed just under the drop of glue, blow through the straw onto the drop of glue (CAUTION: be sure to exhale and not inhale) and spread the glue over the developed latent print. Completely cover the print so that a bit of glue extends just over the edges of the fingerprint. More or less glue can be used to accomplish additional tests on lifting your print in subsequent attempts at this technique; the amount will depend on your liking.

Allow the glue to dry completely over the print. In the field, use incandescent lighting to accelerate the process.

Once the glue has dried over the fingerprint, take your sharp-pointed knife tip and lightly cut or score around the edges of your fingerprint; thus making it easier to lift. Care should be taken not to damage the fingerprint; just a very light scoring is all that is needed.

Next, place your wide Scotch tape over the glue-covered fingerprint. You may wish to lightly rub the tape down on the surface of the glue. Do not stick your tape firmly down as if you expect it to stick to the tablecloth.

Then, pull back on the Scotch tape from one end back over to top of the glued fingerprint. This should pull the dried glue off of the surface of the table cloth with the latent print and glue attached to the tape. Carefully re-tape your latent print and drop of glue onto a piece of white paper to preserve the print and enter it into evidence.

Repeat this methodology several times until you become proficient at recovering a latent print from a rough-textured surface. Post your synopsis as described above on the Discussion Board so that others may read and comment on your Lab. Good Luck!!