Buccal Cells and Saliva as Sources of Evidence in Forensic Investigation — Assistant Lecturer Hwaida Nazzal Hussein Epithelial cells line the inside of the mouth, and shed cells together with other genetic material may enter saliva samples. The mouth is therefore an important source of reference samples and biological traces on used objects. This connects cell biology with forensic investigation by explaining DNA availability and distinguishing contributor identity from trace type and transfer circumstances. Saliva-related traces may occur on drinking cups, cigarette ends, or other objects. However, finding DNA on such an item does not independently establish saliva as its source. The material may originate from handling or transfer from another source. Identifying the body fluid therefore requires appropriate examination and cannot be inferred solely from the object’s shape or customary use. Buccal swabs are used to collect reference samples for genetic comparison under procedures that establish the donor’s identity and document collection. Reference samples serve a different purpose from unknown traces. The former provide profiles of known origin, while the latter require assessment of location, condition, and possible mixing. Keeping these roles separate supports organization, contamination prevention, and clear comparison. Examination begins with photographing the object and documenting sampling locations. Separate areas may need separate collection because the rim, outer surface, and handling region can carry traces with different contexts. The specialist selects a collection plan according to the question and object, limiting sample consumption and preserving opportunities for complementary testing where needed. In a hypothetical educational example, investigators recover a cup from a relevant location. One sample produces a profile consistent with a particular individual. This supports possible contribution to the collected material, but it does not establish that the person drank from the cup during the incident. Investigators review site use, earlier presence of the cup, handling by others, witness information, and reasonable alternatives. Studies of saliva-derived DNA transfer highlight the importance of conditions such as moisture and surface properties. These findings show why a trace should not automatically be reduced to one direct contact. Indirect transfer, however, is also not a universal explanation. It is a possibility requiring realistic assessment against the available evidence and case circumstances. Cell biology helps explain the origin of genetic information, while body fluid testing, handling records, and context support its interpretation. Findings become more useful when separate questions are addressed clearly: what material is present, who may have contributed it, and how might it have arrived? Saliva and buccal cell examination can thus provide valuable information without converting genetic correspondence into unsupported proof of use timing or the activity that produced the trace.