If you intend to go for further qualifications, a professional certification takes about 1 year or more. Forensic anthropologists must be highly analytical and have an understanding and appreciation of the scientific method, as well as for the criminal justice system and legal process.
Techs may also offer their expertise as independent forensic science consultants. A forensic science technician may work in the field, in the laboratory, and in a legal setting. Both typically work a hour week, though some crime scene investigators work late-night or early morning shifts.
While crime scene investigators work at crime scenes and collect evidence, forensic science technicians work in laboratories and examine the evidence that has been collected for possible clues about what happened and who might be responsible for the crime. It could also mean that it has to do with the courts or legal system. A crime scene investigator CSI , sometimes called a forensic detective or forensic investigator, is responsible for collecting and securing evidence from a crime scene.
Forensic investigation typically includes the following: Collecting and documenting physical evidence. Taking photographs of crime scenes. Begin typing your search term above and press enter to search.
Press ESC to cancel. Skip to content Home What is the importance of forensic chemistry? Ben Davis May 31, These materials may be part of a criminal case, such as accelerants in an arson investigation; or they might be part of a civil lawsuit, where a complainant is trying to prove a defendant's liability for damages. Their work is particularly important in determining the presence of controlled substances, such as cocaine or marijuana, and finding the origin of a particular batch of drugs.
Identifying the nature of the evidence brought from a crime scene is only the beginning. Forensic chemists must also characterize the results and determine how they fit the big picture of solving a crime or providing a solid defense, as explained by the Bureau of Labor Statistics. For instance, a forensic chemist not only needs to identify the type of paint found at a crime scene -- such as the paint traces in a hit-and-run accident -- but she also must determine how the paint traces arrived at the scene and whether they can be linked to the defendant.
If a case goes to trial, forensic chemists are often asked to give critical testimony as expert witnesses, as explained by the American Chemical Society. Ultraviolet UV spectrophotometry helps distinguish between samples of proteins and nucleic acids such as deoxyribonucleic acid DNA.
Nuclear magnetic resonance spectrophotometry NMR makes use of the fact that nuclei of some molecules absorb radio frequency radiation in strong magnetic fields. Nuclei in certain molecules absorb radiation at characteristic frequencies, making the identification of even tiny or impure samples possible.
X-ray analysis allows the forensic investigator to visualize foreign objects within the body. In neutron activation analysis, a beam of neutrons from a nuclear reactor is directed at a sample of test material. This technique has made possible the determination of arsenic in the hair of corpses buried for hundreds of years. In one case, the body of an Arctic explorer who had died under suspicious circumstances during the s was found buried in a coffin surrounded by ice.
Neutron activation analysis of hair from the body showed that hair that was several centimeters long contained little arsenic, but that shorter hair closer to the scalp which had grown in the few days before death contained high levels of arsenic, indicating that death was probably caused by arsenic poisoning.
Often, the presence of very small impurities makes comparison possible. For example, cars are painted with paints prepared to certain specifications of color and composition, and pigments and binders used vary from one manufacturer to another and even between models from the same distributor. A small sample of paint left at the scene of an accident may be checked for color by spectrophotometry and then analyzed for composition.
Residues left by burning powder from firearms consist of patterns of particles that have both characteristic physical and chemical properties. Burned powder, for example, usually contains traces of nitrites that yield chemical reactions and traces of metals such as barium that are often present in primers.
Both chemical reactions and microscopic analysis including electron microscopy are employed in the identification of powder residues on clothes and skin. An early method for detecting gunshot residue on the hands of suspects involved coating the hand with melted paraffin , allowing the paraffin to cool, and then stripping it off. Gunshot residues transferred from skin to paraffin turned blue or green in the presence of diphenylamine, but many common substances such as urine gave a false positive test.
The Greiss reagent is much more definitive, and additional tests can identify traces of lead around bullet holes. Even microscopic particles are found to have definite compositions and can be unequivocally identified. Toxicologists examine a wide range of materials such as blood stains, urine, and blood gases for traces of poisons or drugs. Many businesses now require the drug screening of employees; it is the responsibility of the technician to distinguish between the presence of illegal drugs and metabolites from foods such as poppy seeds.
Such tests may be as simple as paper or thin-layer chromatography or as complicated as gas chromatographic or electrophoretic and serological analysis of a blood sample.
Following death by unknown cause, samples of the victim's lungs, blood, urine, vitreous humor, and stomach contents are examined for traces of poisons or medication. Insects found on or near corpses are also collected and examined; they may actually absorb traces of drugs or poisons from the body, and in fact, traces of poisons sometimes are found in the surrounding insects long after concentrations in the body have fallen below detectable limits.
Forensic biochemists perform blood typing and enzyme tests on body fluids in cases involving assault, and also in paternity cases. Even tiny samples of blood, saliva, or semen may be separated by electrophoresis and subjected to enzymatic analysis. In the case of rape, traces of semen found on clothing or on the person become important evidence; the composition of semen varies from person to person.
Some individuals excrete enzymes such as acid phosphatase and other proteins that are seldom found outside seminal fluid, and these chemical substances are characteristic of their semen samples. The presence of semen may be shown by the microscopic analysis for the presence of spermatozoa or by a positive test for prostate specific antigen.
In cases of sexual assault, tiny samples of DNA in blood, semen, skin, or hair found on the victim may be purified and the amount of DNA increased by the use of a polymerase chain reaction to produce quantities large enough to analyze.
Since DNA is as specific to a person as fingerprints, matching the DNA of a perpetrator to a sample found on a victim is considered to be proof of contact. Many perpetrators of crimes have been convicted and many innocent persons set free after years in prison as a result of DNA analysis.
Accidents caused by intoxicated drivers kill nearly 15, persons a year in the United States alone almost half of fatal auto accidents are alcohol-related , so a Breathalyzer kit is standard equipment in most police squad cars or state patrol vehicles. Breathalyzers are used to estimate the blood alcohol content of drivers suspected of being intoxicated; the driver may appear sober, but still have a blood alcohol level above the legal limit. Although it is impractical to take blood samples on the highway, research has shown that the concentration of ethanol in the breath bears a definite relationship to its concentration in blood.
Many communities have now set a legal limit of 0. In fact, authorities now consider that a person's driving ability is probably impaired at a blood ethanol level of 0. Several types of analytic devices are available to administer Breathalyzer tests.
One test makes use of a portable infrared spectrophotometer, another uses a fuel cell, and the most common test employs several glass or plastic tubes and some common chemical reagents. The person being tested blows through a tube, which bubbles the breath through a solution of chemicals containing sulfuric acid, potassium dichromate, water, and silver nitrate.
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