Forensic Science under the Microscope Quiz

Answer: Locard's Exchange Principle.

Edmond Locard (1877-1966) set up the first laboratory to apply current scientific methods to criminal investigations in Lyons during 1910. At that time, his equipment was limited to a microscope and a simple spectrometer. His idea that a perpetrator could be tied to the crime scene through cross-transfer of often microscopic evidence (e.g. threads from clothes) during contact soon led to great international interest in the fledgling forensic sciences. One famous case involved identifying suspects in a lucrative coin counterfeiting ring through minute metal particles in their clothing. Over the next two decades, police laboratories were established in many cities throughout Europe. In 1932, FBI Director, J. Edgar Hoover ordered the establishment of a national forensic laboratory to support police activities across the USA.

However, credit for the theory underpinning forensic science should at least be shared with the Austrian judge and prosecutor, Hans Gross (1847-1915) who in 1893 wrote the first treatise outlining how the scientific method might be applied to criminal cases.

Answer: Forensic Entomology.

Forensic entomology is the use of insect and arthropod evidence in criminal investigations. It has three main subfields: i) In Medico-legal entomology the focus is on violent crime and death investigations; ii) Urban entomology deals with the damage done to urban structures by insects; and iii) Storage entomology is concerned with the presence of insects in foodstuffs.

The first documented case using forensic entomology occurred in China in 1235 and can be found in the book 'The Washing Away of Wrongs' by Sung Tz'u (also known as Song Ci). He tells the story of a village where a badly cut inhabitant had been found murdered. The presiding magistrate first tested different types of knives on an animal carcass to determine which type of weapon had been used. After concluding that it was a sickle, he had all the villagers gather in the village square where their sickles were laid on the ground in the hot sun. After a while, a group of blow-flies all gathered on one particular sickle. The owner of the sickle broke down and confessed to the murder. Upon investigation, it was found that the blow-flies had been attracted to some blood and tissue matter which had remained on that sickle.

Answer: Forensic Odontology.

Forensic Odontology is the evaluation of dental evidence that can establish the age, race, sex, dental history and perhaps the occupation of the deceased, as well as providing insight into their status in life. Additionally, a forensic dentist evaluates bite marks on the victim (or other evidentiary objects) and compares the bite pattern to that of the accused (if there is one).

Bite mark evidence on victims was used to convict Rev. George Burroughs during the Witch Trials in Salem, MA, in 1692. He was subsequently hanged. However in 1870, despite evidence that suspect Ansil Robinson's teeth matched the five bites on his murdered mistress, Robinson was allowed to go free.

By 1890, bite evidence was finally regarded as a legitimate scientific discipline. One of the first murder convictions based on bite marks was in the 'Gorringe Case' in 1948 when bites on a breast were matched to the dentition of the suspect.

In 1975, in the case of California vs Marx, evidentiary standards were set for forensic dentistry. Those standards were used as part of the successful 1978 conviction of serial killer, Ted Bundy.

Answer: Fingerprints

In 1910, Thomas Jennings shot and killed Clarence Hillier in his home and escaped the scene. He was detained by police for questioning later that night. Unfortunately for Jennings he had grabbed hand railings outside the Hillier house which had been recently painted and left behind an imprint of four fingers of his left hand. Again unfortunately for Jennings, he had a previous conviction for burglary and had a fingerprint card on file with the police. The fingerprints matched. His trial was the first murder case in the United States in which fingerprints were admitted as evidence. Four experts gave evidence that affirmed the match. On 22 December 1911, Jennings was convicted and sentenced to hang. His appeal to the Supreme Court of Illinois was based on the admissibility of fingerprints as evidence. However, the Supreme Court found that fingerprint evidence was a means of legally identifying individuals and established the acceptance of such evidence in the legal system.

Fingerprints are the tiny ridges, whorls and valleys found on the tip of each finger which develop while the baby is in the womb. During the 1880s, Sir Francis Galton proposed that no two individuals have the same fingerprints. He devised both a method of distinguishing fingerprints which contained similar patterns and a method for grouping them. From this, the science of dactyloscopy, the art of fingerprinting, developed. It is said that the chance of two people's fingerprints matching is one in 64 billion.

Answer: True

Forensic Anthropology applies the knowledge of the physical, social and cultural development of human beings to legal matters, mainly through the examination of skeletal remains. Similar to fingerprints, every skeleton presents a unique bone profile which tells a story of the age, sex, ethnicity and life of the person. It is even possible in certain cases to deduce the career of the person from the development of certain bone structures. There are recognized and established skeletal variations arising from age, gender and ethnic group which scientists use in their investigations. It has been said of Forensic Anthropology that the story is "written in the bones".

A relatively new field of study, Forensic Anthropology was first formally recognized in the 1930's when it was used to assist the FBI in its fight against organized crime.

Answer: Deoxyribonucleic Acid (DNA).

Variation in DNA from person to person is less than 0.1%, yet this is sufficient to distinguish individuals with a high degree of certainty. The closeness of a DNA match between samples can be used to indicate familial groups, with monozygotic ('identical') twins sharing the same DNA. There was great excitement in early 2013 when DNA testing was used to show that a body exhumed from under a Leicester car park was truly that of the last Plantagenet King, Richard III, who died at the Battle of Bosworth in 1485. DNA from Richard's remains was a close match to that of Michael Ibsen, a living descendant of Richard's sister, Anne of York. Another famous case involved disproving the claim Anna Anderson made that she was the Grand Duchess Anastasia. DNA from stored samples of her tissues were no match with that of living Romanov descendants. The first person convicted of a crime (rape and murder) based on DNA evidence was British baker Colin Pitchfork in 1987.

The chances of any two people in the community having the same DNA is approximately two in 1000. However this is entirely due to the proportion of identical twins. If a person doesn't have an identical twin, the probability of finding someone else with the same DNA (assayed using now standard molecular analysis techniques) is about one in 100 billion.

Answer: Trace element composition.

The very small, 'trace' amounts of a large number of chemical elements can be used as a 'fingerprint' to identify the origins of a material in a forensic case. For example, glass is made from silica (silicon and oxygen) but contains very small amounts (parts per million) of uncommon elements like rubidium, barium, strontium and uranium (and many others). The exact composition depends on the origin of the source material (e.g. which mine it came from) plus the manufacturing process and equipment. The ratios of these trace elements to each other is diagnostic. One of the most famous cases where such information has been used is the unsolved question of who shot President Kennedy. Bullet fragments taken from the scene (including the victims) were later analyzed for silver and antimony content. Evidence presented to the 1977 US House of Representatives Select Committee on Assassinations on the trace concentrations of these metals demonstrated that only two bullets hit the car and its occupants. This finding was consistent with the Warren Commission findings but did not prove them to the exclusion of other interpretations.

This same trace element 'fingerprinting' has been used to identify the source of metal fragments used in terrorist bombs and hit and run accidents, the location from where soil samples on a suspect's shoes originated and the provenance of old coins, amongst a myriad of other applications.

Answer: Breathalyser.

The 'breathalyser' involves blowing into a tube which then conveys your breath into a small reaction chamber containing the powerful oxidizing agent, chromium (VI). Any ethanol (alcohol) in your breath results in some of the yellow chromium (VI) being reduced to blue-green chromium (III). This change in color is then detected. The more alcohol in the breath, the larger the color change.

This test is only indicative as there is significant variation in personal responses, hence it is not useful from a legal perspective. However, if this initial screening test proves positive, then a quantitative, forensic blood analysis is then performed. Perhaps contrary to popular belief, drinking coffee does not change the amount of alcohol in the blood and hence is not a way to 'beat the breathalyser'! The alcohol in the bloodstream, related to the amount ingested while drinking, is broken down at a fixed rate by an enzyme, alcohol dehydrogenase, in the liver. Caffeine does not change this breakdown rate.

Answer: An accelerant in an arson case.

Gas chromatography (GC) requires that the forensic sample to be analyzed is in the gas phase, hence it is most suitable for samples which easily can turn into gases (volatile compounds). This forensic gas sample, often containing a large number of volatile components, then passes through a long column where separation of individual components occurs. After separation, each component is then individually identified, usually by a second instrument called a mass spectrometer. Hence it is a two stage process: separation, then identification.

Common applications include identifying accelerants (e.g. gasoline) in fires, explosives in bombings and some drugs. Heating other samples (e.g. paint fragments from car accidents) to high temperatures (pyrolysing) can produce characteristic gas samples that then can be analysed using this equipment.

Answer: She was killed by a dingo.

One vital piece of evidence that led to Lindy's conviction was the 'arterial blood spray' found under the dashboard of the family car. The prosecution alleged Lindy had cut her daughter's throat in the car, then disposed of the body. The chemical test for blood was positive. What was not brought out in the initial trial is that this same Luminol test also shows positive for several other substances (it is not specific just for haemoglobin in blood). One such substance is copper. The Chamberlains lived at Mt Isa in Queensland, right in the middle of a huge copper mining area. Subsequent investigation showed that this 'false positive' was caused by traces of copper, some iron oxide sound deadening paint and a spilled milkshake. A far better procedure would have involved several confirmatory tests for blood: Was it adult or foetal blood (there are subtle but measurable differences in the type of haemoglobin present)? Was it human or animal blood (determined by a precipitin test)? In addition, vital evidence was misplaced through the trial, indicating a complete failure of the 'Chain of Custody'.

Lindy Chamberlain did receive financial compensation for wrongful imprisonment, but proper forensic procedures should have ensured that this miscarriage of justice never occurred.