Forensic analysis refers to the scientific examination and evaluation of physical evidence related to a crime or civil dispute. It involves applying analytical techniques from various disciplines, such as biology, chemistry, and physics, to analyze materials like fluids, fibers, fingerprints, DNA, documents, digital data, and toolmarks. The goal is to provide objective information that can establish key facts, reconstruct events, identify suspects or victims, associate or eliminate suspects from contact with a victim or crime scene, and assist the court in rendering a legal opinion. Forensic analysis plays a critical role in criminal investigations and justice by helping investigators and legal teams establish the truth through scientific evidence. It has become an indispensable part of the modern legal system.
Some of the key types of forensic analysis include:
Trace Evidence Analysis
Trace evidence analysis involves examining small, microscopic particles found at a crime scene to link suspects to the scene or victim. Some common types of trace evidence analyzed include:
Hair analysis: Comparing hairs found at a crime scene to a known sample can indicate whether the hair likely came from the suspect. Analysts examine the morphological characteristics of the hair roots and shafts, such as color, thickness, pigment distribution and damage. This type of analysis is not conclusive, but can provide supporting evidence when used along with DNA analysis. (1)
Fiber analysis: Fibers from clothing, carpets, rope, etc. can transfer between a perpetrator and victim during a crime. Examiners analyze the color, texture, polymer type and microscopic characteristics of questioned fibers compared to known fiber samples. Results can associate a suspect with a victim or crime scene.
Paint analysis: Paint from vehicles, buildings and other sources often transfers during collisions and break-ins. Forensic labs use microscopy, spectroscopy and chromatography to analyze the layers, chemical composition and trace elements of paint samples. This can reveal if paint chips found at a crime scene match the paint on a suspected source.
Glass analysis: Glass fragments from headlights, windows and other sources are often left behind at crime scenes. The density, elemental composition and refractive index of glass can be measured and compared to known samples. Fracture pattern analysis can also reveal if broken glass at a scene matches up with remaining glass from the broken source.
(1) Forensic Criminology. International Journal of Advance Research, Ideas and Innovations in Technology. https://www.ijariit.com/manuscripts/v5i2/V5I2-1317.pdf
Toxicology
Forensic toxicology involves analyzing biological samples for the presence of toxins, drugs, and poisons. According to the National Institute of Justice, forensic toxicology provides critical information in death investigations and impaired driving cases. The analysis is conducted on blood, urine, hair, and other samples collected from a decedent or suspect.
Some of the key applications of forensic toxicology include:
- Drug and alcohol testing – Analysis can detect the presence and concentration of alcohol, illicit drugs like cocaine and heroin, and prescription medications. This helps determine if substance use contributed to a death or impaired driving.
- Poison analysis – Identifying poisons like cyanide, ricin, and heavy metals helps establish homicide, suicide, or accidental poisoning as the cause of death.
- Drug facilitated crimes – Date rape drugs like Rohypnol can be detected long after administration to help prosecute sexual assault cases.
- Workplace drug testing – Urine and hair analysis helps employers enforce drug-free workplace policies.
According to the NIST Primer on Forensic Toxicology, modern methods like chromatography and mass spectrometry allow for precise identification and quantification of drugs and poisons in minute concentrations. This increases the reliability of conclusions drawn from toxicology results.
Overall, forensic toxicology provides critical evidence by detecting the presence and concentration of intoxicating or toxic substances in biological samples collected from decedents and suspects.
DNA Analysis
DNA analysis has become a pivotal tool in forensic investigations. It allows investigators to identify individuals by comparing their unique DNA profiles. According to the article Thirty years of DNA forensics – C&EN by CH Arnaud[1], DNA profiling methods have evolved rapidly, becoming faster and more sensitive.
There are two main types of DNA analysis used in forensics – STR analysis and mitochondrial DNA testing. STR (short tandem repeat) analysis examines nuclear DNA by looking at specific regions or loci that are highly variable between individuals. By analyzing multiple STR loci, investigators can generate a DNA profile that is extremely discriminating. STR analysis can successfully identify individuals even from small or degraded biological samples.
In cases where nuclear DNA is limited or unavailable, mitochondrial DNA (mtDNA) testing may be used instead. mtDNA is passed down maternally and does not change between generations. This type of testing is good for establishing familial connections and identifying ancestral lineage. While not as discriminating as nuclear DNA, mtDNA analysis provides useful leads when nuclear DNA evidence cannot be recovered.
Overall, the evolution of DNA analysis techniques has greatly enhanced forensic investigations. As techniques become even faster and more sensitive, DNA is likely to continue revolutionizing how crimes are solved.
[1]Arnaud, C. H. (2017). Thirty years of DNA forensics – C&EN. C&EN Global Enterprise, 95(37). https://cen.acs.org/analytical-chemistry/Thirty-years-DNA-forensics-DNA/95/i37
Fingerprint Analysis
Fingerprint analysis involves analyzing fingerprints left behind at a crime scene to identify suspects. Fingerprints have unique ridge characteristics that allow examiners to match them to specific individuals. Fingerprint analysis has been used for over 100 years and is the most commonly used forensic technique.
Fingerprint classification systems organize prints based on their patterns. The most widely used system classifies prints into loops, whorls, and arches. Automated fingerprint identification systems (AFIS) provide computer databases that can match fingerprints found at crime scenes to known prints on file. AFIS provides a fast, automated way to compare millions of fingerprints and identify suspects through fingerprint evidence.
While fingerprint analysis has been a foundational forensic technique for decades, recent studies have shown some limitations in accuracy and reliability. One study found false positive rates between 7-96% among examiners analyzing matching fingerprints (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3093498/). Factors like complex patterns or distorted prints can increase errors. Overall though, modern fingerprint scanning technology can provide accuracy rates over 99% in controlled conditions (https://www.bayometric.com/how-accurate-are-todays-fingerprint-scanners/). Fingerprint evidence should be carefully analyzed and considered along with other evidence in an investigation.
Firearms & Toolmarks
Firearms analysis involves the examination of ammunition components, including bullets, cartridge cases, shotshells, and wadding, to identify the firearm used in a crime. Toolmark analysis examines toolmarks left on objects at a crime scene to identify the specific tool that was used.
When a firearm is discharged, it leaves unique microscopic markings, called toolmarks, on the bullets and cartridge cases. By examining these toolmarks under a comparison microscope, firearms examiners can determine whether two bullets or cartridges were fired from the same firearm. The Association of Firearm and Tool Mark Examiners (AFTE) has developed a methodology for making comparisons and reaching conclusions about bullet and cartridge case evidence.
Some key aspects of bullet and cartridge case comparisons include:
- Class characteristics – Features determined by design factors like caliber, type of firing pin, and number of lands and grooves.
- Individual characteristics – Random, microscopic imperfections caused by use, abuse, and normal wear and tear.
- Consecutively matching striae – Consistent groups of parallel lines across two surfaces, indicating a common source.
Through these comparisons, firearms examiners can potentially link a bullet or cartridge case to a specific firearm as the source. Studies have shown firearm and toolmark analysis to be a valid and reliable forensic discipline (see Scientific American).
Toolmark analysis follows similar principles to compare marks left on objects at a crime scene to a suspected tool. Some tools that may leave identifiable marks include hammers, screwdrivers, crowbars, and wire cutters. By analyzing the class and individual characteristics in the toolmarks, forensic examiners can potentially identify the specific tool used in the commission of a crime.
Document Analysis
Document analysis involves the examination of documents to identify authorship and authenticity. Some of the key techniques in document analysis include:
Handwriting analysis: Forensic handwriting examiners analyze the characteristics of a person’s handwriting, such as the shapes of letters, writing slant, letter connections, and spacing. This can be used to identify forgeries and match writings to suspects in crimes [1]. Famous cases cracked through handwriting analysis include the Lindbergh kidnapping and the Zodiac killer.
Typewriting analysis: Forensic document examiners can identify the make and model of typewriters based on characteristics of the typeface and defects in individual letters. This allows documents to be traced back to a specific typewriter. Printing and photocopier identification can also be used to trace documents.
Printer identification: Printers leave distinctive marks on documents based on the technology, model, settings, and mechanical parts. Examiners can use these patterns to trace documents back to a specific printer [2].
Fax identification: Faxes undergo image compression and can pick up defects during transmission. Forensic analysts can use these compression artifacts and defects to identify the fax machine used to transmit a document.
Computer Forensics
Computer forensics focuses on extracting, decrypting, and analyzing data from electronic devices such as computers, smartphones, and digital storage media. Computer forensics experts extract data while adhering to chain of custody procedures to preserve and identify evidence for use in legal proceedings. Some key aspects of computer forensics include data extraction, decryption of encrypted files and devices, and network analysis to identify where data may have traveled or been stored.
Data extraction involves retrieving active files, archived files, deleted files, temporary files, registry data, internet history, and other forms of data from storage media. Experts use specialized software tools and hardware write blockers to prevent modification of data during the imaging process. Decryption may be necessary for encrypted files, devices, or network traffic. Network analysis enables tracing data flows across networks to identify external storage locations.
Forensic Accounting
Forensic accounting involves analyzing financial records to detect and investigate financial crimes or fraud. Some of the most famous forensic accounting cases have involved major corporate scandals and financial frauds.
One of the biggest forensic accounting cases was the Enron scandal in 2001. Enron, an energy company, used complex accounting tricks to hide billions in debt and make the company appear profitable when it was not. Forensic accountants found evidence of fraud and corruption at the highest levels of Enron’s management.
Another major case was the financial fraud committed by Bernie Madoff. Madoff ran a massive Ponzi scheme and defrauded investors out of billions of dollars over several decades. Forensic accountants unraveled the complex web of lies in Madoff’s financial records and transactions.
More recently, forensic accountants uncovered a major accounting scandal at the UK retailer Tesco. Tesco had been overstating its profits for years through aggressive accounting tactics. Forensic analysis found evidence that Tesco’s leadership deliberately inflated earnings.
Forensic accountants play a vital role in detecting financial crimes and bringing the perpetrators to justice. Their analysis of financial records provides critical evidence of wrongdoing in major corporate scandals and fraud cases.
Conclusion
Forensic analysis plays a crucial role in criminal investigations and legal proceedings. As we have seen, there are several key types that provide critical evidence and insights:
Trace evidence analysis examines materials like hair, fibers, glass, soil to link suspects and victims to crime scenes.
Toxicology identifies drugs, alcohol, poisons to determine cause of death or impairment.
DNA analysis compares genetic profiles from blood, bodily fluids, hair to identify individuals with scientific certainty.
Fingerprint analysis matches fingerprints found at crime scenes to suspects and victims.
Firearms and toolmarks analysis analyzes ammunition, weapons, tools to link them to crimes.
Document analysis verifies authenticity and exposes forgeries through handwriting, typewriting, inks, paper.
Computer forensics examines digital devices and technology to uncover evidence.
Forensic accounting investigates financial records to uncover frauds, embezzlement, money laundering.
As technology advances, we can expect continued improvements in analysis techniques. Emerging areas like digital forensics will become even more critical. But the fundamental principles of thoughtful analysis and linking evidence to events will remain at the core of forensic science.