Today's Veterinary Practice provides comprehensive information to keep every small animal practitioner up to date on companion animal medicine and surgery as well as practice building and management.
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| VETERINARY FORENSICS Projectile Wounds • Projectile wounds—arrows, bullets, pellets, and shot— may be perforating, having both entrance and exit lesions. These "through and through" wounds should be carefully examined to differentiate the entrance from the exit wounds. • Radiographs may help locate projectiles within the remains if there is no demonstrable exit wound. • Black powder stippling (tattooing) and bruising of the skin around an entrance wound may indicate a firearm discharged at close range.29 • Any projectiles or casings (bullet coverings) should be recovered with plastic or soft-tipped forceps to avoid interfering with the rifling pattern. The rifling pattern is essential evidence that matches projectiles to the same firearm.29 Stabbings • Careful consideration and examination of the external wound and wound track characteristics can provide information about the type of weapon used. • Various techniques exist for following a wound track. » The more common method is to gently probe the tract with a pliable object than dissect tissues » A second method is to dissect surrounding tissues (flap method). • Probing and attempts to follow penetration tracks must be done carefully to avoid destroying or creating false evidence. • Consideration of the depth and breadth of the wound may allow scientific elimination of some weapons. Toxicology Toxins are chemical agents derived from a biological source (eg, botulinum, anthrax). Poison is a more general term that includes toxins and chemically derived poisons (eg, ethylene glycol, potassium cyanide, rodenticides). Some common poisons seen in malicious crimes against animals include strychnine, cyanide, ethylene glycol, corrosives, human pharmaceutical agents, carbon monoxide, illicit and illegal drugs (eg, amphetamines, heroin, cocaine), and rat poisons (eg, difacinone, bromodialone, bromethalin, cholecaciferol, carbamate).17,30,31 Toxicology testing should be considered in all cases where it cannot be definitively ruled out.32,33 Analytical test results may yield sufficient information for a search warrant or even a conviction in some courts. Any request submitted to the toxicology analytic laboratory should include all antemortem signs, medical records, postmortem information, and the suspected class of poison. As mentioned earlier, evidence should be prepared in accordance with laboratory protocol and appropriate forensic principles. THE NEGATIVE NECROPSY The negative necropsy is one where, after both gross examination and histopathologic examination, no conclusive cause of death is found.34,35 Reasons for a negative necropsy include: • Failure to obtain a thorough and complete medical history and/or investigation findings 46 Today's Veterinary Practice July/August 2013 SAFEty & PRotECtIon DuRIng FoREnSIC nECRoPSIES Forensic examination of animals is not without risk. Personal safety must supersede all necropsy procedures. • Safety includes use of nonporous gloves, clothing, and equipment that isolates the examiner from zoonotic disease, poisons, and toxic gas.38 • Thenecropsyshouldbeperformedinanisolated, well ventilated area away from patients and susceptible humans. • Inhalation of, or skin contact with, formalin and other preservatives, even in dilute forms, should be avoided. • Failure to complete a detailed external or internal examination • Failure to complete appropriate histopathologic tissue collection • Improper storage of remains. However, sometimes significant external or internal signs or lesions may be absent, and the necropsy may be negative despite best efforts for correct processes. In these cases, additional toxicologic or specialized histochemical analyses may be needed to confirm a cause of death.34,36 For this reason, it is prudent to maintain duplicate tissue samples, appropriately stored for follow-up testing. The negative necropsy doesn't indicate "defeat" since a thorough necropsy, with appropriate testing, may corroborate or contradict evidence contained in police, witness, or crime scene reports. The negative necropsy may present a significant challenge to the veterinarian's credibility as an expert witness, and therefore, must be directly addressed in any forensic report. There are now trends in the field of human necropsy for negative findings to be followed by genetic testing to identify precursor risk factors that may explain the death.37 These techniques are not currently used in veterinary medicine but may be developed for future use. IN SUMMARY The goal of this article is to educate the general practitioner about the significant issues related to the forensic, medicolegal necropsy. This information does not replace FInAnCIAl ConSIDERAtIonS The ability to pursue forensic and/or scientific testing is dependent on the physical and financial resources of the investigating veterinarian and law enforcement agency. Submitting samples through chain of custody protocol may add hundreds of dollars to otherwise identical biomedical testing. The investigating veterinarian should always consult with the lead investigator or prosecutor before pursuing testing.