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 facts:
- Friction ridges develop on the fetus in their definitive form prior to birth.
- Friction ridges are persistent throughout life except for permanent scarring, disease, or decomposition after death.
- Friction ridge paths and the details in small areas of friction ridges are unique and never repeated.
- 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 ear print, 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.
Since forensic identification has been first introduced to the courts in 1980, the first exoneration due to DNA evidence was in 1989 and there have been 336 additional exonerations since then. Those who specialize in forensic identification continue to make headway with new discoveries and technological advances to make convictions more accurate.
Body identification is a subfield of forensics concerned with identifying someone from their remains.
Feet also have friction ridges like fingerprints do. Friction ridges have been widely accepted as a form of identification with fingerprints but not entirely with feet. Feet have creases which remain over time due to the depth it reaches in the dermal layer of the skin, making them permanent. These creases are valuable when individualizing the owner. The concept of no two fingerprints are alike is also applied to foot creases. Foot creases can grow as early as 13 weeks after conception when the volar pads begin to grow and when the pads regress, the creases remain. When foot crease identification is used in a criminal case, it should be used in conjunction with morphology and friction ridges to ensure precise identification. There is record of foot crease identification used in a criminal case to solve a murder. Sometimes with marks left by the foot with ink, blood, mud, or other substances, the appearance of creases or ridges become muddled or extra creases may appear due to cracked skin, folded skin, or fissures. In order to truly compare morphological feature, the prints of feet must be clear enough to distinguish between individuals.
The two basic conceptual foundations of forensic identification is that everyone is individualized and unique. This individualization belief was invented by a police records clerk, Alphonse Bertillon, based on the idea that "nature never repeats," originating from the father of social statistics, Lambert Adolphe Jacques Quetelet. The belief was passed down through generations being generally accepted, but it was never scientifically proven. There was a study done intending to show that no two fingerprints were the same, but the results were inconclusive. Many modern forensic and evidentiary scholars collectively agree that individualization to one object, such as a fingerprint, bite mark, handwriting, or ear mark is not possible. In court cases, forensic scientists can fall victim to observer bias when not sufficiently blinded to the case or results of other pertinent tests. This has happened in cases like United States v. Green and State v. Langill. Also, the proficiency tests that forensic analysts must do are often not as demanding to be considered admissible in court.
There are many different applications for wildlife forensics and below are only some of the procedures and processes used to distinguish species.
Species Identification: The important of species identification is most prominent in animal population that are illegally hunted, harvested, and traded, such as rhinoceroses, lions, and African elephants. In order to distinguish which species is which, mtDNA, or mitochondrial DNA, is the most used genetic marker because it's easier to type from highly decomposed and processed tissue compared to nuclear DNA. Additionally, the mitochondrial DNA has multiple copies per cell, which is another reason it's frequently used. When nuclear DNA is used, certain segments of the strands are amplified in order to compare those to segments of mitochondrial DNA. This comparison is used to figure out related genes and species proximity since distant relatives of animals are closer in proximity in the gene tree. That being said, the comparison process demands precision because mistakes can easily be made due to genes evolving and mutating in the evolution of species.
Determination of geographic origin: Determining the origin of a certain species aids research in population numbers and lineage data. Phylogenetic studies are most often used to find the broad geographic area of which a species reside. For example, in California seahorses were being sold for traditional medicinal purposes and the phylogenetic data of those seahorses led researchers to find their origin and from which population they came from and what species they were. In addition to phylogenetic data, assignment tests are used to find the probability of a species belonging to or originating from a specific population and genetic markers of a specimen are utilized. These types of tests are most accurate when all potential population's data have been gathered. Statistical analyses are used in assignment tests based on an individual's microsatellites or Amplified Fragment Length Polymorphisms (AFLPs). Using microsatellites in these studies is more favorable than AFLPs because the AFLPs required non-degraded tissue samples and higher errors have been reported when using AFLPs.
Domestic animal forensics
Domestic animals such as dogs and cats can be utilized to help solve criminal cases. These can include homicides, sexual assaults, or robberies. DNA evidence from dogs alone have helped over 20 criminal cases in Great Britain and the U.S. since 1996. There are only a few laboratories though that are able to process and analyze evidence or data from domestic animals. Forensics can be used in animal attacks as well. In cases like dog attacks, the hair blood, and saliva surrounding the wounds a victim has can be analyzed to find a match for the attacker. In the competitive realm, DNA analysis is used in many cases to find illegal substances in racehorses by urine samples and comparisons of STRs.
- Color copiers and maybe some color computer printers steganographically embed their identification number to some printouts as a countermeasure against 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. DNA marking.)
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