Animal evidence (Forensic Science)
The animal evidence involved in cases of crimes against humans most often consists of shed hairs and traces of blood, other body fluids (including saliva and urine), and excrement from either dogs or cats. Given that in the United States about 40 percent of households include at least one dog and 30 percent include at least one cat, crime scene investigators frequently encounter this kind of evidence.
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Animal Hair (Forensic Science)
In relation to crimes against humans, the most commonly analyzed type of animal evidence is shed hair. Research has shown that it is almost impossible for a person to enter a house where a dog or cat lives and not have some of the animal’s hair transferred to his or her skin, shoes, or clothing. Criminal perpetrators who live with dogs or cats can thus transfer the hair of their animals to victims or crime scenes. Perpetrators can also pick up animal hairs from crime scenes, from victims’ clothing, from household items, or directly from victims’ pets.
In 1994, white hairs from a cat named Snowball were used to help convict a Canadian man of murdering his wife. police investigators found the hairs on the husband’s black leather jacket. This was the first evidentiary use of nonhuman DNA (deoxyribonucleic acid) to help solve a crime. In this case, the DNA analysis used feline microsatellite markers mapped by English geneticist Alec Jeffreys. Scientists have concluded that both feline and canine microsatellite markers are almost as discriminating as their human counterparts, not very much diminished by the inbreeding often seen in canines.
Because shed hair lacks a viable root, it usually does not contain enough nuclear DNA to allow short tandem repeat (STR, or microsatellite) fingerprinting of individuals. Instead, criminalists extract and amplify mitochondrial DNA (mtDNA) from the hair shaft, which contains thousands...
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Other Types of Animal Evidence (Forensic Science)
Animal blood found at crime scenes usually contains enough viable nuclear DNA for STR analysis, which can be used to identify an individual animal. As early as 1998, STRs obtained from dried canine blood linked a suspect to the murder of a Seattle couple and the killing of their dog. Although the suspect was convicted, the canine DNA evidence was not admitted at trial because canine DNA typing was not considered reliable at the time. Since then, the reliability of canine and feline STR profiling has been well established in the scientific literature, and dog and cat DNA evidence is regularly admitted in legal proceedings.
Both urine and excrement from dogs have also provided nuclear DNA to help solve crimes and convict criminals. One example of using DNA from animal fecal matter outside the legal justice system is the identification of the Canadian lynx from scat found near the large cat’s paw prints in snow. This technique is being investigated as a way to track the health, distribution, and population densities of certain endangered animal species.
The National Fish and Wildlife Forensics Laboratory in Ashland, Oregon, is dedicated to the collection and analysis of evidence of crimes against wildlife. Law-enforcement agencies submit to the lab the types of animal evidence discussed above in addition to more unusual samples, such as hunting trophies (antlers), carved ivory, hides, furs, bones, teeth,...
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Further Reading (Forensic Science)
Cassidy, Brandt G., and Robert A. Gonzales. “DNA Testing in Animal Forensics.” Journal of Wildlife Management 69 (October, 2005): 1454-1462. Discusses how animal DNA is being used to solve human crimes. Gives examples from specific legal cases and notes the potential pitfalls related to DNA processing and collection methods.
Cooper, John E., and Margaret E. Cooper. Introduction to Veterinary and Comparative Forensic Medicine. Ames, Iowa: Blackwell, 2007. Includes discussion of wildlife conservation and links between cruelty to animals and violence toward humans. Intended for veterinarians and law-enforcement officials but written at a level understandable by interested laypersons.
Dorion, Robert B. J., ed. Bitemark Evidence. New York: Marcel Dekker, 2005. Comprehensive collection of essays on all aspects of the study of human and animal bite marks. Well illustrated.
Merck, Melinda D. Veterinary Forensics: Animal Cruelty Investigations. Ames, Iowa: Blackwell, 2007. Readable work discusses the handling of suspected animal cruelty cases.
Saferstein, Richard. Criminalistics: An Introduction to Forensic Science. 9th ed. Upper Saddle River, N.J.: Pearson Prentice Hall, 2007. Classic introductory text includes discussion of animal-related evidence.
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Animal Evidence (World of Forensic Science)
Evidence of animals, especially animal hair, is often discovered at crime scenes. Pet or other animal hairs can be found on the clothes of the victim or on other items of physical evidence collected at the crime scene. The identification and analysis of human and animal hairs from a crime scene can indicate physical contact between the victim and a suspect, or provide other investigative leads. Transferring of pet hairs to the victim, to a suspect, or to the crime scene may happen when the perpetrator is a pet owner (or when the victim owns a pet), or when the crime was committed in a place where animals are kept, such as barns, stables, basements, or transport vehicles.
Through microscopic analysis, hairs can be identified as belonging to a particular species of animal. In the case of a known suspect, animal hair identified on the victim's clothing can be compared to hairs found either in the suspect's home, car, or clothing in search of a match. If the pet of the victim or of the suspect is available, further forensic analysis can be made to confirm whether that particular pet is the source of the hair in question. The pet's bed or brush can also provide samples for such identification.
When human remains are found outdoors, forensic procedures are conducted to establish whether the cause of death was due to homicide, suicide, accident, animal attack, or natural illness (i.e., heart attack, stroke, or other pathological condition). Perforation wounds, bullet holes, blunt force injuries, and other lesions normally point to a criminal act as the cause of death. However, animal access to corpses may cause such destruction of the remains that the real cause of death can be impossible to determine in certain cases. Animals feeding on a dead body leave distinct marks on bones and tissues. The signs of wild carnivores and scavenger birds, for instance, are recognizable through characteristic marks left on the bones and soft tissues by claws, fangs, and beaks. Nevertheless, even bodies found in urban areas or inside doors can suffer animal destruction by rodents and domestic animals, such as dogs and ferrets.
Forensic anthropologists are experts in determining the gender, race, and age of unrecognizable remains (usually by studying the bones) and in identifying what kind of animal activity was responsible by the destruction of those remains. Bodies of drowned individuals found on seashores or riverbanks can also display signs of animal activity, such as from crabs or fish.
Animal evidence in human remains has been systematically registered and studied since 1943, including the action of a variety of species, such as wild dogs, large cats, bears, cows, horses, poisonous snakes, marine animals, constricting snakes, rodents, birds, and domestic dogs. The types of injuries and typical feeding behaviors of various species are also well documented. One of the indications of animal scavenging on human remains involves bones or body parts that are scattered, such as a skull found some distance from the body, with teeth lost after death. This is common in bodies left on the surface or buried on shallow graves in woods or country areas. Missing body parts or bones are often retrieved from dens of coyotes, foxes, or skunks along tracks and pathways used by these animals.
The types of postmortem marks left on human remains by animals allow the identification of the species involved because of the known specific anatomical features and feeding behavior of each species. Seagulls, crows, owls, and other carrion-eating birds leave puncture wounds in the flesh, caused by their hard sharp bills. Vultures damage bones with their talons and beaks as they remove the flesh. Coyote, fox, and other wild and domestic canids puncture, tear, and crush the soft tissues by gnawing and shaking their heads, splintering bones, and leaving jagged bone edges through the action of their posterior teeth. Rodents have sharp paralleled incisors that leave parallel furrows in flesh and bones, with a pattern of layered destruction of tissues. Big cats leave v-shaped punctures from their canine teeth, claw slashes, and abrasions, and great amounts of crushed and splintered bones. Big cats, wolves, and wild dogs have a preference for eating the internal organs first, therefore eviscerating the body. Domestic dogs also can eat human remains when they are hungry, causing great destruction of the corpse. Such situations can pose extra challenges to forensic investigators in determining the circumstance, time, and real cause of death.
SEE ALSO Anthropology; Crime scene investigation; Death, cause of; Evidence; Microscope, comparison; Skeletal analysis; Taphonomy.