Collecting Fingerprints Target 2-3 Thursday, October 26, 2017

Target 2-3 I can match fingerprints by collecting, classifying, and analyzing them.

Collecting Print Samples Crime Scene Suspects Victim Controls

Crime Scene Prints Visible Prints Finger came in contact with a colored material such as blood, paint, ink To collect: Take photos

Crime Scene Prints Plastic Prints Physical impression (3-D) in a soft substance such as wax, clay, putty, soap, nail polish To collect: Take photos

Crime Scene Prints Latent Prints Invisible prints left when friction ridges transfer oils from skin to a surface Collection technique depends on the surface

Dusting Apply a fine powdery dust to a surface Use for smooth surfaces Dust will stick to oils from the print Excess dust can be knocked loose or blown away Use for smooth surfaces Glass, plastic Can be done at the scene

Cyanoacrylate Fuming Expose the surface to cyanoacrylate vapor (superglue!) Fumes will stick to oils from the print Fumes will appear white when dried Use for small, smooth objects Glass, plastic Must fit in a small chamber for fuming Object must be transported to the lab Fuming must be done in an enclosed chamber

Iodine Fuming Expose the surface to iodine vapor Fumes will stick to oils from the print Captured fumes will turn brown Use for semi-porous surfaces Skin, cardboard Object must be taken to a lab Fuming must be done in an enclosed chamber Iodine is expensive and toxic

Ninhydrin Spray or soak surface in ninhydrin Use on porous objects Ninhydrin will react chemically with proteins in skin oils Chemical product turns purple when dry Use on porous objects Paper, fabric Must be done in a lab Sample must soak and dry for 24 hours

Silver Nitrate Spray surface with silver nitrate solution Silver nitrate reacts with salt in skin oils Chemical product appears black under UV light Use for porous surfaces Paper, walls, furniture Can be done at the crime scene Silver nitrate residue is toxic and must be cleaned up later