Forensic Science HQ

Investigate the forensic science world

Forensic Trace Analysis

Forensic Trace Analysis the analysis of paint, accelerants, glass or chemical debris.  This type of evidence is most commonly involved in arson and vehicular homicides.  Some forensic laboratories also consider the analysis of microscopic hair and fiber evidence part of the trace chemistry discipline.

Air samples or fire debris are often brought to the laboratory and analyzed for the presence of an accelerant, indicating an intentionally set fire.   Trace chemical analysis can also be performed on debris from an explosion to determine which type of explosive may have been used.  The forensic scientist will use a variety of instruments, including microscopes, x-ray diffraction, gas chromatography, infrared spectroscopy and energy dispersive x-ray micro-analysis.

Hit and run accidents often leave behind a transfer of paint or other chemical materials from one surface to the next.   The forensic trace analyst is often asked to analyze the paint to determine the possible origin, including the make and  model of the originating vehicle.   If a suspect is identified, the analyst may need to compare the evidence sample to a “known” sample from the suspect vehicle to determine if the two samples “match”, and could share a common origin.

In addition to fire, explosion and paint debris, forensic trace analysis could include the chemical analysis of virtually any other type of evidence.  This could include items such as duct tape, cosmetics, concrete, fabric, soil, and gunshot residue.

Questioned Documents

A forensic scientist specializing in questioned documents usually work cases involving alleged forgery, blackmail, kidnapping and death threats.

Although questioned documents examiners are often referred to in the media as “handwriting experts”, they frequently examine evidence with no hand writing at all.  These items may include printed materials, typewritten documents, photographs, and duplicated productions (copies).   It is often the task of the document examiner to determine if the item in question has been altered, forged, or obliterated.  This requires the use of special light techniques, most commonly infrared or ultraviolet light.  Inks and printing appear differently under certain light depending on their chemical composition and the amount of force applied to the medium.  It is therefore possible to determine if more than one utensil has been used to produce a document and if more than one technique or source has been used.

forensic questioned document

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For example, a common tactic among forgers is to alter a legitimate check and increase the amount of the draft.  A check for $100 may appear to have changed to read $10,000.  By examining the check under alternate light sources, it can sometimes become very obvious that a two different pens were used to add the additional zeros to the amount.  This type of analysis is photographed and can easily be demonstrated to a jury should the case go to trial.

In the case of handwriting analysis, it is possible to prove that a specific individual did or did not write the document in question.   This is done by obtaining “known” samples of handwriting from the person of interest and comparing those samples to the piece of evidence.   The examiner will look at individual strokes, loops, spacing , and slant.   Determining that someone is NOT the source of a document is often times easier and quicker than concluding that an individual is the source.  In addition to using alternate light sources in their analysis, the question document examiner will also often use various microscopes, including comparison scopes and even electron microscopes.

In addition to handwriting and printed materials, the document examiner may also be asked to perform impression analysis.  This may include evidence involving rubber stamps, gloves, footwear and tire impressions,  indented writing and tool marks, glove impressions, and footwear and tire impressions.
Training to become a question document examiner takes several months and involves case studies and laboratory exercises.   The forensic document examiner must frequently work in close conjunction with latent print examiners, as there is often times a need for fingerprint analysis on the evidence as well as document analysis.

forensic document

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Individuals interested in a career as a document expert should expect slow, methodical work and must be able to explain their analysis to a jury that often confuses the science behind this type of work with the erroneous perception that is a subjective art.   Forensic Questioned Document examiners are not the same as handwriting hobbyists who assign personality traits to various writing styles or to profiling experts who analyze the content and psychological meanings of criminal evidence.

Forensic document examiners in a criminal laboratory determine if a piece of evidence has been altered, obliterated, forged, or otherwise tampered with and who may or may not be responsible for the document based on careful comparison between it and known samples.

Famous cases in the United States that involved question document analysis include the “Unibomber”, the “Zodiac Killer”, and the Jonbonet Ramsey homicide.

 

Educational Requirements for a Forensic Scientist

Forensic Scientists are considered experts in their field and often must testify in court to explain their analysis and the significance of their findings. To become a forensic scientist requires continual learning, however for those just starting a career in forensic science, a Bachelor’s Degree in any field is often acceptable. An advanced degree or an emphasis in science classes is beneficial to the initial hiring process.

Forensic Science Educational Requirements

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Due to the rising popularity of forensic science brought about by several successful television series, several colleges and universities are now offering courses specializing in forensics and legal studies. These courses can certainly help you when you look for a job as a forensic scientist but they are not required. Certain specialties in forensic science require specific classes, for example, Genetics, Biochemistry and Organic Chemistry are required for DNA analyis. If you are interested in a becoming a forensic scientist, it is best to check with nearby forensic laboratories before applying to see if they have any advice for you that may be unique. Laboratory experience is also helpful in addition to a degree, even if it’s not in a forensic lab. Some agencies offer internships which is an excellent way to get started.

A “discipline” refers to a specialized area of expertise in forensic science. Examples of disciplines are question documents, fingerprint analysis, DNA analysis, and drug chemistry. Most forensic laboratories enroll scientist in their own training program designed for their discipline immediately after hiring. Everything about the forensic specialties is taught to the trainee after they are hired. Laboratories strive to have a certain number of scientists with advance degrees. For example, laboratories accredited with ASCLD require that a lead DNA analyst have a minimum of a master’s degree. So while it’s possible to be hired with only a Bachelor’s degree, those with a Master’s or phD do have an advantage.

If you are interested in becoming a forensic scientist, the first thing you need to do is learn about the various disciplines and descide which one intests you. Contact the forensic laborartory in your area and ask about their requirements and hiring opportunities. Forensic labs are found in nearly all states and privately owned laboratories exist as well. On a national level in the United States, the Federal Bureau of Investigation (FBI) operates a forensic science laboratory and hires trainees as well.

A good education is required to become a forensic scientist and it’s crucial to take your studies seriously if you want to succeed. A career in Forensic Science is highly competitive and very demanding. Not only are good grades important, but you must also be willing to continue your education throughout your career.

Forensic Chemistry


Forensic Chemistry, or “Drug Chemistry” is the forensic discipline of identifying evidence thought to be a controlled substance. Most often, the types of evidence the forensic drug chemist examines are pills, capsules, plant materials, tables, powder, drug paraphernalia and residues.

drug chemistry

Drug Chemistry

When an individual is prosecuted for possession or distribution of a controlled substance, the degree of the punishment and offense is often directly related to the amount of drugs identified in the case. It is the job of the drug chemist to accurately weigh the amount of substance, using a balance and then positively identify the drug in question.

The evidence is inventoried, often times photographed, and tested with a one or more techniques, including traditional spot tests, thin layer chromatography (TLC) and extraction, as well as instrumental techniques such as ultraviolet (UV) spectroscopy and gas chromatography (GC).

Forensic Drug Chemistry

Marijuana is frequently examined.


Advanced techniques such as Infrared spectroscopy (IR) or mass spectrometry (MS) are used to confirm the identity of questioned substances. Microscopy is also available for examining case material, such as marijuana. A report is issued to the investigative agency identifying any controlled substances amount detected. The Forensic Chemist is often required to testify as an expert in court to describe the methods used and the conclusions that were reached.