Forensic science applies scientific methods to evidence so investigators can better understand what happened, when it happened, and how different clues may be connected.
Forensic scientists examine evidence using methods from biology, chemistry, physics, medicine, computing, and other scientific fields. Their job is not to guess or decide guilt. Instead, they document evidence, perform controlled tests, compare results, and explain what the science does and does not support. Reliable forensic work depends on careful procedures, accurate records, quality controls, and conclusions that stay within the limits of the evidence.
Photographs, notes, measurements, and careful collection preserve information before evidence is moved.
Learn MoreRidge patterns can be documented and compared when suitable prints are recovered from a surface.
Learn MoreBiological material can sometimes provide a DNA profile that helps compare individuals or samples.
Learn MoreChemical tests and instruments can help identify unknown substances and compare materials.
Learn MoreTiny materials such as fibers, glass, soil, or paint can sometimes connect people, objects, and places.
Learn MoreGood forensic science uses validated methods, controls, documentation, and careful interpretation.
Learn MoreBefore evidence is collected, investigators often document a scene with photographs, sketches, measurements, written notes, and location information. This creates a record of where objects were found and how the area looked at the time of examination. Evidence must then be packaged and labeled in ways that reduce contamination, loss, or mix-ups. A written record called a chain of custody tracks who collected, transferred, examined, and stored each item so its history can be reviewed later.
The skin on human fingers contains raised friction ridges that form patterns such as loops, whorls, and arches. Fingerprints can be left behind when sweat and other substances on the skin contact a surface. Examiners may use powders, chemicals, special lighting, or digital imaging to make some prints easier to see. A useful print can then be compared with known prints by examining ridge details, but poor or incomplete prints may not contain enough information for a strong conclusion.
DNA is found in most human cells, so biological material such as blood, saliva, or skin cells may contain genetic information. In many forensic laboratories, scientists examine selected regions of DNA that vary among people and use those results to create a profile. A DNA profile can support or exclude a possible match when enough suitable material is available. Because DNA can be transferred or contaminated, scientists must use controls, protective equipment, careful collection methods, and cautious interpretation.
Forensic chemists use laboratory methods to study unknown powders, liquids, residues, inks, fuels, and many other materials. Some tests produce a quick indication of what a substance might be, while more specific instruments can separate a mixture and identify its chemical components. Scientists compare measured properties with known reference materials and record the limits of each method. A result is strongest when it comes from validated procedures and can be checked independently.
Trace evidence refers to small materials that may be transferred when people, objects, or places come into contact. Examples include fibers, hair, fragments of glass, paint chips, soil particles, and tiny pieces of plant material. Microscopes and other instruments can reveal features that are difficult to see with the unaided eye. Trace evidence often helps scientists compare samples or reconstruct possible contacts, but a shared material does not automatically prove exactly when or how that transfer occurred.
Forensic science is most dependable when laboratories use methods that have been tested, documented, and shown to perform reliably for their intended purpose. Scientists use positive and negative controls, equipment calibration, peer review, proficiency testing, and detailed case notes to reduce errors. They also need to report uncertainty and avoid claiming more than the evidence supports. These safeguards matter because scientific evidence may influence important decisions, so transparency and careful reasoning are essential.