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Forensic Biology in Samples and Examples
Forensic science entered our lives couple years ago when CSI television series start showing. I admit, they caught my attention instantly and I became addicted to the latest mysteries in front of Gil’s or Horatio’s team of experts. Most people I know are fascinated by high tech laboratories and sophisticated evidence collecting techniques that could be seen in every episode. If you put familiar faces from the show aside, forensic can be defined as application of diverse scientific methods and knowledge to solve legal issues (crimes or civil actions). Disciplines such as paleontology, chemistry, biology, botany, osteology, odontology…are widely used during crime investigation.

Forensic biology is what fascinates me the most. Every crime scene is associated with more or less biological materials. Blood, urine, semen, saliva, hair, skin….those are true markers of the crime. They can be analyzed in various ways and used for different purposes.

Hair can be analyzed using the polarized light microscope; it can be source of DNA (hair follicle) or can link suspect or some third person with crime scene. Species specific differences in hair structure can be easily recognized once hair is under the microscope. Also, hair can be used for drug screening as some substances could be found in hair 90 days after consumption.

Blood is probably the most common bodily fluid seen at the crime scene. To be sure that its blood we are looking at, small amount of Luminol is usually splashed. It reacts with blood by bonding with iron from hemoglobin. Positive result (indicating presence of blood) will be obvious by blue glow in darkened environment. Bloodstain pattern analysis is also very helpful during the investigation. Blood is usually main source of both victim’s and suspect’s DNA. To exclude animal derived blood, test with human antigen is applied. Once you confirm human origin, blood type and DNA analysis could be performed. DNA profiling is technique used to identify person. It’s like finger printing – each person has its unique DNA. Although people share 99.9% of the same genetic material, differences in DNA pattern are still big enough to distinguish one person from another. Variable number tandem repeats (VNTRs) analysis is used for that purpose. VNTR are groups of two of more nucleotides that are repeating continuously on different chromosomes. Their length is variable. VNTR analysis provides evidence of genetic similarity between samples because “variants” are completely different between unrelated individuals and highly similar between close relatives. Toxicological analysis is used to detect presence of drug that could be responsible for any kind of poisoning. Gas chromatograph-mass spectrometer is most often used method for separation (if the mixture of chemicals is present), differentiation and quantification of the substances in the blood sample.

Urine can be easily detected on the cloths or some part of the furniture because it becomes fluorescent under UV lights. It is mostly used for toxicology screening as all chemicals are metabolized and excreted eventually by urine. Urine drug test kits are used for quick and efficient detection of certain chemicals in field (in situ) or in laboratory. Here’s the list of drugs that could be easily detected (with 99% accuracy) in just a couple of minutes using some of the marketed drug kits: marijuana, cocaine, opiates (like heroin), methamphetamine, ecstasy, amphetamine, phencyclidine, tricyclic antidepressants, barbiturates, benzodiazepines, methadone, oxycodone.

Alpha amylase is enzyme present in saliva at high doses and thus widely used as indicator of hidden saliva at the crime scene. Saliva can be collected easily and it’s highly accurate in detecting illegal substances in traces (that can be found in saliva while circulating the body). Saliva is popular and often used DNA source. Epithelial cells from the inner lining of the mouth are “equipped” with the same genetic material (both in quality and quantity) as DNA from the rest of the body.

Semen on the crime scene is mostly associated with sexual assaults. It is highly fluorescent and can be detected with UV lamp. Lab method used to confirm presence of sperm is best known as Christmas tree stain (because of the bright colors seen under microscope). DNA from the sperm is used for DNA fingerprinting and suspect identification.

Beside described biological material, teeth and bones are used for personal identification and age and gender determination.

Forensic science is combining most interesting methods from various scientific disciplines. If you have quick mind, cold blood and enough will to get necessary knowledge you can become next forensic expert. Maybe it’s not the cleanest and easiest jobs to do, but at least it’s humane.
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That is great piece of information , indeed. I would like to say that i got to learn a lot of things out of it. There were few things which i didn't know about and it helped me to know about it.
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