Ch 14 Fingerprints part 2

AFIS AFIS There was a manual system in place Cumbersome system of storing, retrieving, & searching for prints 1970 now can classify and retrieve prints by computers Very skeptical and hesitant at first Automated fingerprint identification system Automatic scanning devices that convert the image of a fingerprint into digital minutiae that contain data showing ridges at their points of termination (ridge endings) & the branching of ridges into 2 ridges (bifurcations) There was a manual system in place AFIS

AFIS More to it The trained expert Relative position & orientation of minutiae are determined; computer stores each fingerprint in form of digitally recorded geometric pattern Search algorithm determines degree of correlation Can make thousands of fingerprint comparisons in a second Makes final verification of print’s identity

AFIS How it operates Benefits $ A system within it filters out imperfections in latent print, enhances image, creates a graphic representation Print is computer searched against file prints Image of latent and match displayed side-by-side Spend less time developing suspect lists More time investigating suspects generated by computer Need to be cautious of those prints not in system yet Database that is created and managed, do have to pay to have access to it

Methods of detecting Visible prints Plastic prints Latent (invisible prints) Made by fingers touching surface after ridges been in contact with colored material Ridge impressions left on soft material Impressions caused by transfer of body perspiration or oils present on finger ridges

Detecting Latent Prints Locating the invisible Hard & nonabsorbent surfaces (glass, tile, etc) apply a powder or treat with Super Glue Soft & porous surface (paper, cardboard, cloth) require treatment with chemicals New technology - Reflected UV Imaging System - UV image converter helps to find latent prints w/o chemicals

Preservation of Developed Prints Photograph Taking print to lab Must be taken once print has been visualized Photos also need to be taken to provide overall view of print’s location w/ respect to crime scene Option 1 wrap in cellophane and take whole thing Option 2 use powder, then lift with tape and placed on labeled card