DNA recovery and STR profiling from heated tobacco sticks for forensic personal identification

"Heated tobacco products" (HTPs), featuring a heating blade placed either in the holder (HH) or within the stick itself (EH), are increasingly being used. The composition and mode of consumption, along with the possible reduction in salivation induced by their use, could affect DNA recovery and STR profiling. The aim of this work was to assess the DNA recovery useful for personal identification from two commercially available types of HTP sticks, compared with traditional cigarettes. Sixteen volunteers each smoked 2 traditional cigarettes, 2 HTP sticks of type HH and 2 HTP sticks of type EH each (n = 96). For each type, one filter paper was analyzed immediately (T0), and another after one month of storage in a controlled environment (T1). DNA amounts ranged from 0.265 to 7.4294 ng/μl for traditional cigarettes and 0.0008 ng/μl to 6.4711 ng/μl for HTP sticks, showing a significant difference (p = 0.0092). DNA recovery from traditional cigarette, but not from HTP sticks, was significantly lower at T1 compared to T0. Ninety-two samples (95.8%) were amplified, yielding 88 full STR profiles (95.6%), 4 partial profiles (4.4%) and 5 mixed profiles (5.4%), while no profiles deemed inconclusive. Mixed profiles likely resulted from persistent DNA transferred prior to the controlled conditions. Heated tobacco sticks may lead to lower DNA recovery than traditional cigarettes, potentially impacting other forensic DNA analyses that require higher DNA yield than STR profiling.