Persistence of touch DNA on burglary-related tools

Abstract

Experts are increasingly concerned by issues regarding the activity level of DNA stains. A case from our burglary-related casework pointed out the need for experiments regarding the persistence of DNA when more than one person touched a tool handle. We performed short tandem repeat (STR) analyses for three groups of tools: (1) personal and mock owned tools; (2) tools, which were first "owned" by a first user and then handled in a burglary action by a second user; and (3) tools, which were first owned by a first user and then handled in a moderate action. At least three types of tool handles were included in each of the groups. Every second user handled the tool with and without gloves. In total, 234 samples were analyzed regarding profile completeness of first and second user as well as properties like detectable major profile or mixture attributes. When second users simulated a burglary by using a tool bare handed, we could not detect the first user as major component on their handles but attribute him to the stain in 1/40 cases. When second users broke up the burglary setup using gloves, the first user matched the DNA handle profile in 37% of the cases. Moderate use of mock borrowed tools demonstrated a material-dependent persistence. In total, we observed that the outcome depends mainly on the nature of contact, the handle material, and the user-specific characteristics. This study intends to supplement present knowledge about persistence of touch DNA with a special emphasis on burglary-related cases with two consecutive users and to act as experimental data for an evaluation of the relevance of alleged hypotheses, when such is needed in a court hearing.

DNA detection of a temporary and original user of an office space

“…Whilst duration, frequency and manner of contact (including contact points and levels of pressure and friction) will have impacted the profiles observed [21,26,27], it is likely that the shedder status [17,[28][29][30][31][32] of the office owners and temporary occupants will also have impacted the profiles generated. For example, while the shedder status of the participants in this study is unknown, the temporary occupants of O1 and O4 in Lab A, and O1 in Lab B, were rarely present on the tested items within the offices they occupied, whereas the office owners were the sole or major/majority contributor to profiles from most items (thus the office owner may be a good shedder and/or the temporary occupier a poor shedder).…”

DNA transfer in forensic science: A review

“…However, in other studies where the circumstances were less controlled and/or optimised, the non-self component of the transferred profile was the major or only contributor in no more than 3% of samples [63,75,123,139,142,143].…”

“…Furthermore, the level of interaction (from a single static contact of a specific sub-area of an object, to multiple, frequent, varied manners and locations of contact) of a handled object with another object will also vary widely. A study by Pfeifer and Wiegand [123] demonstrated the impact of different intensities of handling a tool (intense mock break-in to a premises versus normal use of a tool according to its designed purpose) on the types of profiles subsequently collected.…”

“…If items possessing background DNA are then used by others (i.e. the offender) during the course of an alleged criminal activity, mixtures from the usual user and offender can be expected [27,82,104,[123][124][125][126][127][128]. For example, a study of background levels of DNA on common burglary entry points from 20 different premises (windows, doors) found 26% (n=150) produced a DNA profile [129].…”

“…Personal items and clothing are often collected as evidentiary or reference material. It is usually assumed that these will provide the profile of the regular user/wearer, which they usually do; however, they often also contain DNA from other sources [64,82,104,123,137,[160][161][162][163][164]. For example:…”