Forensic identification is the application of forensic science, or "forensics", and technology to identify specific objects from the trace evidence they leave, often at a crime scene or the scene of an accident. Forensic means "for the courts".
People can be identified by their fingerprints. This assertion is supported by the philosophy of friction ridge identification, which states that friction ridge identification is established through the agreement of friction ridge formations, in sequence, having sufficient uniqueness to individualize.
Friction ridge identification is also governed by four premises or statements of fact:
1. Friction ridges develop on the fetus in their definitive form prior to birth.
2. Friction ridges are persistent throughout life except for permanent scarring, disease or decomposition after death.
3. Friction ridge paths and the details in small areas of friction ridges are unique and never repeated.
4. Overall, friction ridge patterns vary within limits which allow for classification.
People can also be identified from traces of their DNA from blood, skin, hair, saliva and semen by DNA fingerprinting, from their teeth or bite by forensic odontology, from a photograph or a video recording by facial recognition systems, from the video recording of their walk by gait analysis, from an audio recording by voice analysis, from their handwriting by handwriting analysis, from the content of their writings by their writing style (e.g. typical phrases, factual bias, and/or misspellings of words), or from other traces using other biometric techniques.
Body identification is a subfield of forensics concerned with identify someone from their remains.
Color copiers and maybe some color computer printers steganographically embed their identification number to some printouts as a countermeasure of currency forgeries.
Copiers and computer printers can be potentially identified by the minor variants of the way they feed the paper through the printing mechanism, leaving banding artifacts. Analysis of the toners is also used.
Documents are characterized by the composition of their paper and ink.
Firearms can be identified by the striations on the bullets they fired and imprints on the cartridge casings.
Paper shredders can be potentially identified in a similar way, by spacing and wear of their blades.
Photo identification is used to detect and identify forged digital photos.
Typewriters can be identified by minor variations of positioning and wear of their letters.
Illegal drugs can be identified by which color it turns when a reagent is added during a color test. Gas Chromatography, Infrared Spectrometry or Mass Spectrometry is used in combination with the color test to identify the type of drug.
Cars can be automatically found on CCTV records by automatic number plate recognition.
Computers connected to the Internet can often be identified by their IP address or MAC address.
Radio transceivers can be potentially identified by minute variations of their output signal.
Social networks can be discovered by network analysis of banking, telecommunication and postal records.
Sometimes, manufacturers and film distributors may intentionally leave subtle forensic markings on their products to identify them in case of piracy or involvement in a crime. (Cf. watermark, digital watermark, steganography.)