The challenges involved in identifying biological traces include:
• The investigation of bodily fluids such as blood, semen, saliva, etc. in order to reveal their presence in a stain.
• Human/animal-specific tests since the biological sample may belong to animals rather than a human being.
• Body fluid identification tests to determine the anatomical origin of a fluid. For example, blood may derive from the nose, from a skin injury or from the uterus (menstrual blood).
• DNA analysis to identify the contributor of the sample, or to rule out the possibility that the sample belongs to a particular individual (such as the victim or the suspect of a murder, etc.).
These analyses help in the reconstruction of a crime scene or the evaluation of statements released by murder or sexual offence suspects as to the nature of suspicious stains that may be present on their clothing or belongings.
When bloodstains are found, it is necessary to establish their origin. Suspects frequently claim that bloodstains are the result of common accidents (nosebleeds, self-inflicted wounds, etc.) or incurred while carrying out professional duties (such as slaughtering animals) or at home (in the kitchen, etc.).
Requests to examine the origin of stains of possible biological nature are frequently received in private cases. In cases of conjugal infidelity the requests are often for a check on the presence of seminal liquid on clothing. In cases of suspected fraud, as well as threats and boycotts, tests may be requested on items found with biological traces on their surfaces.
From:Cazzaniga, Cattabeni, Luvoni, Zoja.
Compendio di Medicina Legale e delle Assicurazioni.
UTET Giuridica, 2022
Book chapter by A. Piccinini (mod.).
