Development and Collection of Prints

Patent Prints

• What would you do if you found this on the wall of a crime scene?

1. Photograph:a) With scale (ruler)b) Multiple angles and distances

2. Lift using clear plastic tape.3. Document, document, document!4. Store as evidence.

Plastic Prints

• What about this print?

1. Photograph:a) With scale (ruler)b) Multiple angles and distances

2. Take a cast using plaster of paris or other substitute (dental stone).

3. Document, document, document!4. Store as evidence.

Latent Prints Nonporous Surfaces

Surfaces such as laminated or painted wood, tile, plastic, glass, tv screens, metal, firearms, cars…

Dust with Powders:- Adheres to oils,

sweat, etc. - Magnetic powder

- Carbon black, aluminum powders

- Fluorescent powders- ALS

- Lift with tape; place on backing card of appropriate color- Document!!!

• Heat superglue in airtight chamber with water source, vapors settle on amino acids producing polymer and permanent white print.

• Cyanoacrylate Vapor (Super glue):– Best on plastic,

metal, glass.

Latent Prints Nonporous Surfaces

Multiple methods based on target surface

Latent Prints Porous Surfaces

Unlaminated or painted wood, paper, cardboard, cloth

1. Iodine fuming:Best on paper or cardboard or unpainted surfaces.Place print in airtight container with solid iodine.Iodine vaporizes (sublimation: skips liquid phase) and settles on carbohydrates in sweat.FADES QUICKLY: Have to make permanent with starch solution.

• Ninhydrin:– Best on paper

Latent Prints Porous Surfaces

• Spray surface with Ninhydrin spray and place in fume hood.

• Reacts with amino acids (protein monomers) in sweat.

• Reacts mainly with NaCl in our sweat to form silver chloride creating black or reddish-brown print under UV light.

• Silver Nitrate– Best on wood

and styrofoam.

Latent Prints Porous Surfaces