Fingerprints and Impressions Questions and Answers

Answer: B

A latent fingerprint on an electric bulb should be preserved by fixing the bulb in a bulb holder inside a wooden box. The bulb is held firmly and cannot move or touch other surfaces, so the thin print on the smooth glass is not rubbed away in transport.

A cardboard box and a paper bag let the bulb roll or rub against the packing, which smears the print. A cellophane bag is also poor because plastic films can stick to or lift a latent print and trap moisture. The key accepts only the fixed holder.

Answer: D

The official key gives anastomosis. In this description, a ridge forks and then the two branches join again, so that a closed ring is formed and the line continues as one ridge. The key names the rejoining as anastomosis, a word that means a joining together of two channels.

Bifurcation and fork name only the splitting of a ridge into two branches, with no reunion. An island is a short ridge that stands by itself between two others. These three do not describe a split followed by a reunion, so the key's choice is accepted.

Answer: C

The concept of poroscopy, the identification of a person by the number, size, shape and position of the sweat pores on the ridges of the fingerprints, was given by Edmond Locard, the French forensic scientist, in 1912.

Karl Landsteiner discovered the ABO blood groups. Burrard is the author of a work on the identification of criminals by fingerprints, but did not give poroscopy. Hans Gross wrote the Handbuch fur Untersuchungsrichter on criminal investigation and is called the father of criminalistics. Only Locard is linked to pores.

Answer: B

The key takes the layer of cells between the epidermis and the dermis to be the dermal papillae. The upper dermis is thrown into small projections, the dermal papillae, which push up into the epidermis and shape the friction ridges seen on the fingertips.

Minutiae are the ridge details, such as endings and bifurcations, used to compare prints. Sweat pores are the openings of the sweat glands on the ridges. Friction ridges are the raised lines on the surface of the skin. None of these three is a layer between the two skin layers.

Answer: D

Ninhydrin reacts with the amino acids present in a fingerprint residue to give a purple coloured compound called Ruhemann's purple, named after Siegfried Ruhemann, who described the reaction in 1910. It is used to develop latent prints on paper.

Dimethyl formamide is only a solvent. Pervanadyl and vanadyl are compounds of vanadium and have no link with the ninhydrin reaction. Only Ruhemann's purple is the coloured product.

Answer: D

The correct matching is central pocket loop with 3, arches with 1, twinned loop with 4 and lateral pocket loop with 2. A central pocket loop has one core and two deltas. An arch has no delta. A twinned loop has two loops opening at opposite sides of the pattern. A lateral pocket loop has two loops opening on the same side. This is code D, 3 1 4 2.

Option A swaps twinned loop and lateral pocket loop. Option B and option C give arches a delta, which is wrong, since an arch has none.

Answer: B

Both statements are true, option B. A plain impression, in which the finger is pressed on the paper in a single motion, is unsatisfactory for fingerprint analysis, since the ridge detail near the edges is not shown. The reason is true as well, since a plain impression shows fewer points or junctions than a rolled one, which captures the whole pattern from nail to nail. Options A, C and D call at least one true statement false. A rolled impression is taken by rolling the finger from one edge of the nail to the other, so it shows all the ridges, and a plain impression is made by pressing the finger down without rolling.

Answer: C

The finger ridges are formed by rows of sweat pores, option C, in the key's reading. A ridge is made up of a row of pores, from which the sweat that makes the latent print comes out. Dermal cells (A) are cells of the skin, dots or islands (B) are small ridge features, and minutiae (D) are the ridge characteristics, such as bifurcations and ending ridges, rather than what forms the ridge itself.

Answer: C

The key gives the codes 3, 1, 4, 2 (option C). Latent fingerprints are invisible fingerprints (3), patent prints are prints deposited on paint or blood and readily visible (1), plastic prints are formed in a soft material like putty (4), and tap prints are plain fingerprints (2) left when a finger touches a surface lightly. Option A gives latent prints the plain impressions, option B gives them the soft material and option D gives plastic prints the paint or blood, so each of them is rejected.

Answer: C

In primary fingerprint classification, numerical values are given to the whorl patterns, option C. In the Henry system the ten fingers are taken in pairs, with values of 16 for the first two fingers, 8 for the next two, 4, 2 and 1 for the following pairs, and a finger that carries a whorl contributes the value of its pair. The even numbered fingers form the numerator and the odd numbered fingers the denominator of the primary fraction, and one is added to each. Loops and arches carry no value, so they are not given a number, which is why options A, B and D are rejected.