courtesy : Forensic Science
Human identification
Droplets of human blood. In addition to analyzing for DNA, the droplets are round and show no spattering, indicating they impacted at a relatively slow velocity, in this case from a height of two feet.
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. Many methods that are used in forensic science evidence have been proven to be unreliable. A lot of trials have been reviewed and testimony involving mostly microscopic hair comparison, but also bite mark, shoe print, soil, fiber, and fingerprint comparisons have been overturned because forensic analysts have provided invalid testimony at the trial.
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, usually from fingerprint analysis, dental analysis, or DNA analysis.
Foot creases
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.
Downfalls
The two basic conceptual foundations of forensic identification are 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.
