Biotechnology applies biological processes to create products and technologies. This field has transformed various industries by harnessing the intricate mechanisms of life. In legal investigations, forensic science uses scientific principles to analyze evidence. Biotechnology provides powerful tools for examining biological materials, revolutionizing how evidence is collected, analyzed, and interpreted in criminal and civil cases.
Identifying Individuals Through DNA
A significant contribution of biotechnology to forensics is identifying individuals through their unique genetic material, DNA. This process, known as DNA profiling, relies on specific DNA regions that vary greatly among individuals. These highly variable segments, Short Tandem Repeats (STRs), consist of short DNA sequences repeated multiple times. The number of repetitions at specific STR locations differs between people, creating a unique genetic fingerprint.
Forensic scientists collect DNA samples from crime scenes, which can include biological materials such as blood, saliva, hair, or skin cells. After collection, DNA is extracted from these samples. Polymerase Chain Reaction (PCR) amplifies specific STR regions, creating millions of copies of DNA segments. This makes it possible to analyze even minute quantities of genetic material.
Following amplification, the copied DNA fragments are separated by size using a method called capillary electrophoresis, which generates a distinct pattern of peaks. This pattern represents an individual’s unique DNA profile. The profiles obtained from crime scene evidence can then be compared to profiles from suspects or victims. A match indicates that the evidence likely originated from that individual, while an exclusion means it did not.
DNA profiling has become an invaluable tool for linking suspects to crime scenes, identifying unknown victims of disasters, and exonerating individuals who were wrongly accused. In the United States, DNA profiles are stored and compared within the Combined DNA Index System (CODIS). This national database allows law enforcement agencies to compare crime scene DNA profiles against a vast collection of known offender profiles and profiles from other unsolved cases, significantly aiding investigations.
Analyzing Other Biological Evidence
Beyond DNA profiling, biotechnological methods are also used to analyze other biological evidence found at crime scenes. Forensic serology identifies the type of biological fluid present. This involves specific tests to determine if a stain is blood, semen, or saliva, without identifying the individual source at this initial stage.
Immunological tests detect specific proteins unique to human blood, such as glycophorin A. Enzymatic tests identify the presence of amylase, an enzyme indicative of saliva. Identifying the fluid type helps investigators understand the crime and prioritize samples for detailed DNA analysis. These preliminary tests narrow the scope of forensic examination.
Forensic toxicology relies on biotechnology to detect and quantify substances in biological samples. Toxicologists analyze samples like blood, urine, or tissue from victims or suspects to identify drugs, poisons, or harmful chemicals. Initial screening involves immunoassays, which use antibodies to identify specific drug classes.
After screening, precise biotechnological techniques like Gas Chromatography-Mass Spectrometry (GC-MS) or Liquid Chromatography-Mass Spectrometry (LC-MS) are used for confirmation and quantification. These methods separate and identify compounds, providing detailed information about the type and amount of substance. This analysis helps determine the cause of death, assess impairment, or establish drug use in criminal investigations.
New Frontiers in Forensic Biotechnology
Biotechnology continues to advance, opening new frontiers in forensic science beyond traditional DNA identification and fluid analysis. Forensic phenotyping uses DNA to predict the physical characteristics of an unknown individual. When no DNA database match is found, forensic phenotyping can provide investigative leads by predicting traits such as hair color, eye color, and ancestry. This is achieved by analyzing specific genetic markers, known as single nucleotide polymorphisms (SNPs), associated with these observable traits.
Epigenetics is another developing field in forensics. Epigenetic markers are chemical modifications to DNA that do not alter the underlying sequence but can affect gene expression. Analyzing these markers can provide information about a sample, such as the individual’s age or lifestyle factors like smoking habits. Epigenetic analysis can also determine the tissue type of a biological sample, distinguishing between blood and saliva even if both originate from the same person.
Microbial forensics analyzes microbial communities found on evidence. Every person carries a unique microbiome, and these signatures can be transferred to objects or locations. By analyzing bacteria, fungi, and other microorganisms on items like clothing, soil, or human remains, investigators can link individuals to specific environments or trace the origin of biological agents in bioterrorism cases. This approach offers additional information to forensic investigations.