Passage 1

The police force has come a long way since the medieval days when suspected criminals were thrown into rivers to determine whether they were guilty or not. If they floated, they were innocent; if they sank, they were guilty. These days, high-rating TV programmes such as CSI show exactly how sophisticated the tools police use have become, as well as showcase the rise of forensic scientists as part of the police force. A forensic team assists in criminal investigation procedures by drawing on the knowledge of a number of sciences.

One of the most acclaimed forensic experts is Dr Henry Lee, who has been awarded 5 honorary doctorates and has worked on over 6,000 cases, including war crimes in Bosnia and Croatia, the assassination of former US president John F. Kennedy and the suicide of former US President Clinton's White House attorney. The resources he draws on are wide and varied.

Forensic anthropologists are employed for their skill in recovering and examining skeletal remains. These experts apply the methods and techniques developed in skeletal biology and osteology to determine the type of injury sustained, the time of death and the sex, age, height, stature, ancestry and medical history of the victim. For example, the cranium or mandible is often used to ascertain sex and ancestry, the hands and fingers can be used to establish stature and the sacrum confirms age, pregnancy and childbirth in females.

Unlike forensic anthropologists, forensic document examiners can not determine the age or gender of a writer. However, they can determine the source of a letter and when it was written or printed. These professionals analyse handwriting, typewriting, printing, photocopying, ink and paper, and are most commonly employed to closely examine wills, ransom notes, extortion notes, cheques and letters. They are so skilful that they can decipher obliterated or erased writing, burned or charred documents, and even detect alterations.

Entomology, the study of the life cycles of insects, is used in forensic science to determine the amount of time that has elapsed after someone has died. This is a valid method as insects behave predictably. They lay eggs on the exposed surface of a body and the amount of infestation follows certain patterns and time intervals. This method has been applied to child abuse and neglect cases as well as lack of care for wounds existing on the elderly under private or public care.

Fingerprints, like DNA, are used to identify a person. Identical twins do not have identical fingerprints despite having the same DNA. DNA does not change whereas fingerprints may do so due to scarring, skin disease or skin growth. Forensic fingerprinting involves making the prints visible, saving them for further investigation and matching them to existing ones on a huge database of billions of prints from around the world.

Unlike fingerprints, which can easily be washed away, teeth are very resilient and can stay in good shape even after being submerged in water for long periods. As a result, forensic odontology is used to help police identify victims. Ante mortem dental records are compared with those of the deceased. If no dental records exist before death, then these dentists can also narrow down the search by providing authorities with the victim's age, ancestry, sex, socio-economic status and in some instances occupation, diet, habits and diseases.

Forensic serologists examine blood and bodily fluids to determine the nature of stain found at a crime scene, including determining which species the stain belongs to and matching the blood groups, isoenzymes, and DNA patterns to a known sample. To be accurate, it employs techniques and methods applied in immunology, biochemistry, serology, haematology and molecular biology. Blood can determine the sex, age and race of a suspect and wet blood can also be tested for alcohol and drug content. By analysing the antibody profile in blood, we can distinguish between identical twins.

Blood splatter analysis provides vital clues to the police. The height and angle from which the blood fell can be determined by analysing how it splatters. The surface also plays a part in how blood splatters. For instance, blood that hits a smooth, hard surface has very little distortion around the edge. Blood which lands on linoleum flooring distorts somewhat more, while blood that strikes wood or concrete distorts to a much larger extent. The force and direction of a blow can also be ascertained by examining blood smeared on walls or floors.

Forensic chemistry and toxicology analyses unknown chemicals and toxins and attempts to trace them to known substances or identify specific origins. These practices help to identify the cause of death by analysing residues or powders to determine that a gun was fired or explosives were ignited.

Forensic artists put together a composite sketch to help identify a victim or to track down a suspect. This is a complicated profession, as a forensic artist isn't simply an artist. He or she also needs to know about anthropology if reconstructing a face from skeletal remains. If the sketch includes teeth, they also need to know about odontology and if they want to show the effects of ageing, they will need to know about psychology. This science can produce remarkable results. A classic case was that of John Emil List who was caught as a direct result of using a composite photo almost 20 years after killing his family.