Forensic Science

Forensic science is used for many reasons. It can help investigators determine how an accident has occurred, gives clues which can lead to the arrest of criminals and can be used to find out how people died.

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Inst. Of Criminal Science. #7 Dr. G. Everett Marsh-Prof. Forensic Chemistry Makes An Arsenic Compararive Metallic Test. Other Pix Show Major Seth Wiard-Head Firearms Identification Division Doing Comparative Bullet Test On Microscope And Showing James Powell Former Vmi Student, How To Test Bullets, Make Photos Of Them. Also Major Wiard Is Shown Looking Through Instrument That Lights Up Barrel Of Gun For Inspection. Major Wiard's Collection Of Guns From 1779 To Present Day Is One Of Most Interesting In City. (1937-10)LIFE Photo Collection

It is an essential part of providing justice for victims and their families and also vital in improving the safety of vehicles and devices. A forensic scientist’s job is to collect and preserve evidence after a crime or an accident. 

Inst. Of Criminal Science. #7 Dr. G. Everett Marsh-Prof. Forensic Chemistry Makes An Arsenic Compararive Metallic Test. Other Pix Show Major Seth Wiard-Head Firearms Identification Division Doing Comparative Bullet Test On Microscope And Showing James Powell Former Vmi Student, How To Test Bullets, Make Photos Of Them. Also Major Wiard Is Shown Looking Through Instrument That Lights Up Barrel Of Gun For Inspection. Major Wiard's Collection Of Guns From 1779 To Present Day Is One Of Most Interesting In City. (1937-10)LIFE Photo Collection

This evidence is analysed using strict scientific methods and can be used in a court of law to prove innocence or guilt. 

History of forensic science

Most people have a basic understanding of forensic science techniques and think it is a modern science. In fact forensic science has a very long history, dating back to the middle ages. 

The Sickle

The first recorded use of forensic science to prove guilt comes from medieval China in 1325. A farmer was murdered in his field by a sickle (a common harvesting tool). 

Investigators gathered all the sickles and laid them out. One attracted flies, proving it was used in the murder.

Rice detector

In ancient India rice was used to see if a person was lying. The suspect would fill up their mouths with dried rice and made to spit it back out. If the rice stuck in the suspects mouth they would be found guilty, the thought being that lying dried out mouth saliva. 

It’s a match

In 1784 forensic science was used to solve the murder of a maid. Investigators matched a crumpled piece of paper that was used to secure gunpowder with a piece of paper found in the suspect’s pocket. 

Fingerprints

By the mid 1850’s fingerprints were discovered to be unique to individuals. By 1892 the first fingerprint database was established and methods of extracting fingerprints from crime scenes were developed.

Toxicology and ballistics

Toxicology is a branch of forensic science that studies chemicals and their effect on the human body. Ballistics is a branch of forensic science that studies the behaviour of projectiles such as bullets. Both are used extensively in crime investigations in particular. 

Poison

Toxicologists need to understand how each poison can affect people of different sizes, ages and health.  

Stomach contents

The contents of the victim's stomach can help determine the time of death. Investigators know how long the stomach takes to digest food. By seeing how digested food is within the stomach investigators can determine a rough time of death.

Hair samples

Drug use as well as the use of a slow acting poison can be detected by toxicologists. Hair examined under a microscope can tell investigators whether it was naturally shed or pulled out.

Ballistics

Forensic ballistics can tell investigators where in the area a gun was fired, the distance away from the victim and the type of gun used. Examining bullets under a microscope can also match the bullet to the exact gun used.

Trace evidence

Trace evidence are objects left behind after an accident or a crime. These can include bodily fluids as well as objects found within a room such as an overturned chair or a broken window. 

Police will investigate major car accidents and collect trace evidence in order to find out what happened. This will help with determining who is at fault or whether the car itself is faulty.

Photographing the scene

The most important part of collecting trace evidence is to first photograph the scene in situ (on site). Once the site is recorded evidence can be taken away for laboratory analysis.

Skid marks

Skid marks are full of information. They tell investigators how fast the car was travelling at the time of the accident, the steering angle and when brakes were applied. 

Lights

Investigators will study the car's lights to determine if they were on at the time (in the case of headlights), whether brake lights were applied, or whether a turning signal was on (by studying indicator lights).

Debris

The debris created by the accident can be studied and measured to use as evidence. It can indicate the speed of the vehicle, whether other vehicles or other people were involved. Impact points will be recorded as well as the distance items were thrown from the accident. 

Fingerprints

One of the most well known type of trace evidence are fingerprints. Unique to an individual fingerprints can definitively link a person to a scene.

DNA evidence

The introduction of DNA evidence revolutionised the justice system. Many incarcerated people have been found to be wrongly convicted and many criminals have been caught using this type of evidence.

This type of evidence uses a person's unique genetic code to link them to a crime scene (or in some cases exonerate them).

DNA

DNA is a molecule that contains all of an individual's genetic information. DNA is contained in every part of the body including blood, saliva, sweat, mucus, earwax, hair and skin cells. If any bodily material is found at a crime scene DNA information can usually be extracted.

Contamination

Because DNA is easy left at a scene investigators need to be extremely careful when collecting evidence. They need to wear gloves that should be changed after each collection and try to avoid coughing, sneezing or even talking over places where DNA evidence could be found.

Extraction

There are a number of methods used to extract the DNA from the evidence. DNA can be extracted from cigarette butts, drinking glasses, doorknobs and clothing.

Comparisons

DNA alone is unable to identify a person. The suspect’s own DNA is also needed in order to compare the two samples.

Forensic entomology

Entomology is the study of insects. Forensic entomology is the study of insects and how they feed on human remains in order to help solve crimes. 

By Herbert GehrLIFE Photo Collection

Circle of Life

Forensic entomologists understand in great detail the relationship between a deceased human and the insects that feed on the remains. There is a particular order in which each species begins to feed and/or breed on remains. 

Understanding which species arrive when can determine the approximate time of death.

Lab work

Often insects found with remains are taken back to the laboratory for further analysis. By ensuring the exact species is identified (there are over 120,000 species of flies for example) a more accurate time of death can be established.

Accidents

The surprising presence of a spider or a bee in a moving vehicle is believed to be one of the top 20 reasons for car accidents. Forensic entomologists are also sometimes called in to examine squashed insects located on a car to determine the car’s probable path. 

Fire forensics

Fire forensics is used to determine the cause of a fire. As with other forensic sciences fire forensics is used to resolve whether a crime has been committed. Investigators examine whether a fire was deliberately lit or accidental.

Photographic evidence

All branches of forensic science begins by collecting photographic evidence of the scene as it was found by investigators. These photos will be used by fire investigators to study burn and smoke patterns. 

V pattern

Burn patterns can tell fire investigators where a fire originated. There is a distinctive ‘v’ shape that usually appears at the fire’s origin. If for example the v pattern appears above an electrical outlet it could suggest that an electrical fault occurred causing the fire.

Accelerants

Burn patterns are also used to determine whether accelerants were used increase the fire’s spread or ferocity. A ‘u’ shaped pattern can suggest a pool of accelerant was used to start the fire.

Collecting ash

Fire investigators understand how different materials burn under different conditions and fire strength. Ash samples can be collected and analysed to find out what material was destroyed and whether there is accelerant present. 

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