Latent Print Processing Flashcards

Which powder is recommended for developing latent prints on dark-colored surfaces?

Answer: White aluminum powder

White or light-colored powders provide contrast on dark surfaces because the light powder stands out against the dark background.

Small particle reagent (SPR) is used on which type of surface?

Answer: Wet non-porous surfaces

SPR is a suspension of molybdenum disulfide that adheres to fatty residues and is designed for wet or submerged non-porous surfaces.

1,8-Diazafluoren-9-one (DFO) primarily reacts with which component of latent print residue?

Answer: Amino acids

DFO is an amino-acid-reactive reagent that fluoresces under green light excitation, making it useful on porous surfaces before ninhydrin.

Which statement best describes the 'sequential processing' strategy for latent prints?

Answer: Use the least destructive to most destructive methods in order

Sequential processing moves from non-destructive techniques (ALS, photography) through progressively more destructive chemical methods to preserve evidence integrity.

What type of light filter should a photographer use when capturing fluorescent latent prints under ALS?

Answer: Barrier (long-pass) filter that blocks the excitation wavelength

A barrier filter removes the excitation light while passing the longer-wavelength fluorescence emitted by the print, improving contrast in the image.

Luminol is primarily used to detect which substance at crime scenes?

Answer: Blood that has been diluted or cleaned

Luminol reacts with the iron in hemoglobin and produces chemiluminescence, enabling detection of cleaned or diluted bloodstains.

A technician develops a print with ninhydrin on a business card. What color does a positive reaction produce?

Answer: Ruhemann's purple

The ninhydrin-amino acid reaction produces a purple compound known as Ruhemann's purple, which is the classic positive indicator.