Latent Fingerprints Lab Mrs. Pawlowski SUPA Forensic Science Chemistry 113

The purpose of the lab is to perform the techniques and to experience the ways in which forensic scientists gather latent fingerprint evidence.

Recognition of the limitations of the processes will be part of the process.

TABLE A Materials

How do each of these substances/materials reveal latent or hidden prints?

Ninhydrin; reacts with ______to ______.

Black and white (gray) dusting powder; collects on prints because______

Hinge lifters/ and /or tape and backing papers

Clear, black and white backing papers used for ?

Super glue; process to reveal print? Is it permanent?

Iodine crystals/fuming

UV light source

Each of the above techniques will be used to gather, preserve latent prints.

Surfaces tested:

Paper

Glass

Metal

Plastic

  1. You will start with dusting for fp in school. Collect fp on hinge lifters. Preserve the fp with name, date and location.Door glass and window glass and desk top.

Dust samples with black and/or white powder…

Black is carbon- some is volcanic ash powder; the white is aluminum powder.

Do not put anything near your mouth or nose including your fingers.

There is a process to dusting..gentle touch… do not press on the print.

DO NOT need much powder… less is more..

ALL RESIDUE DUST ON SURFACES IN THE BUILDING AND THE CLASSROOM MUST BE CLEANED!

Take paper towels and cleaner as you dust for prints.

Class disturbances, while prowling for prints, is prohibited.

  1. You will use the ultraviolet light source to identify latent prints.

What is the difference between uv light and visible light?

  1. You are to use ninhydrin solution (mixed with acetone)

Do not inhale the fumes directly. Work outside.

  1. Iodine fumes will be used or demo’d. Toxic fumes! Use syringe of solution only- with my assistance.
  1. Super glue will be demonstrated

Conclusions: to be done individually. Cite sources.

  1. What is a fingerprint? What is the residue left behind?
  2. Diagram skin anatomy
  3. What are the friction ridges? Why do humans have friction ridges on fingers and toes, hands and feet?
  4. The chemistry of how thevarious materials from table A, expose, preserve, react to and with substances in the print, must be included in the conclusions of the lab. A chart, table, bullets choice is appropriate.
  5. How does a rough surface, like concrete walkways, affect the latent print and its removal? When would a too smooth surface be a problem for print removal?
  6. How does law enforcement preserve the lifted print? Explain.

Ninhydrin

Black and white dusting powder

Super glue

Iodine crystals/fuming

UV light source

All of the processes above must be included in the conclusion even if the tests are unfruitful in class or we are unable to perform them for lack of technology.

Use the fbi.gov site, World of Forensic Science ebook on the library site and Criminalistics, by Safertstein and delicious.