Relocation of DNA between layers of adhesive tape and other substrates

Adhesive tape is a common piece of evidence that can contain a myriad of traces. Due to its adhesive properties, adhesive tape can potentially collect traces unrelated to the crime or relocate crime-relevant traces. This secondary transfer of traces can have crucial implications for the evaluation at the activity level. Therefore, this study investigated the secondary transfer of DNA between layers of adhesive tape and tape and other case- and laboratory-relevant substrates. A drop of diluted blood was deposited on different primary substrates (i.e. duct tape, metal, plastic, textile, nitrile gloves). Subsequently, the primary substrate was brought into contact with a secondary substrate, and DNA was collected from both surfaces to measure transfer rates. The highest transfer rates were detected between the adhesive side of the tape and plastic, whereas the lowest transfer rates were detected between the adhesive side and textile. It was shown that the adhesive readily collects DNA from plastic and nitrile gloves commonly used in the laboratory, which highlights the importance of working with DNA-free materials. Therefore, this study demonstrated the need for caution when interpreting traces on adhesive tapes, always taking possible situations of secondary transfer into account.