Since the late nineteenth century, fingerprint identification methods have been used by police agencies around the world to identify suspected criminals as well as the victims of crime. The basis of the traditional fingerprinting technique is simple. The skin on the palmar surface of the hands and feet forms ridges, so-called papillary ridges, in patterns that are unique to each individual and which do not change over time. Even identical twins (who share their DNA) do not have identical fingerprints. The best way to render latent fingerprints visible, so that they can be photographed, can be complex and may depend, for example, on the type of surfaces on which they have been left. It is generally necessary to use a 'developer', usually a powder or chemical reagent, to produce a high degree of visual contrast between the ridge patterns and the surface on which a fingerprint has been deposited.

Developing agents depend on the presence of organic materials or inorganic salts for their effectiveness, although the water deposited may also take a key role. Fingerprints are typically formed from the aqueous-based secretions of the eccrine glands of the fingers and palms with additional material from sebaceous glands primarily from the forehead. This latter contamination results from the common human behaviors of touching the face and hair. The resulting latent fingerprints consist usually of a substantial proportion of water with small traces of amino acids and chlorides mixed with a fatty, sebaceous component that contains a number of fatty acids and triglycerides. Detection of a small proportion of reactive organic substances such as urea and amino acids is far from easy.

Fingerprints at a crime scene may be detected by simple powders, or by chemicals applied in situ. More complex techniques, usually involving chemicals, can be applied in specialist laboratories to appropriate articles removed from a crime scene. With advances in these more sophisticated techniques, some of the more advanced crime scene investigation services from around the world were, as of 2010 , reporting that $50 \%$ or more of the fingerprints recovered from a crime scene had been identified as a result of laboratory-based techniques.

1. Which of the following is the best title for this passage?

A In Situ Powder Use in Crime Scene Investigations
B How to Identify a Criminal
C Amino Acids in Fingerprint Detection
D Fingerprint Composition and Detection
E Uses of Papillary Ridge Secretions



Consider all that apply

2. According to the article, amino acids and chlorides in fingerprints originate from the

I sebaceous glands
II eccrine glands
III papillary ridges



3. According to the passage, powders to detect fingerprints are most likely to be used

A instead of reactive organic substances
B at the crime scene
C in laboratories
D to detect triglycerides
E as one of the more sophisticated techniques



4. According to the passage, all of the following are true EXCEPT

A fingerprints identify the victims of crime
B fingerprint patterns may become distorted by sebaceous contamination
C identical twins have different fingerprints
D investigators want to make fingerprints visible so they can be photographed
E touching the face and hair contaminates eccrine gland secretions