Introduction

In criminal investigations, it is crucial to identify individuals present at the scene of a crime or accident and to understand their behavior. We have previously reported that human DNA profiles sufficient for individual identification can be obtained from human-derived environmental DNA (eDNA) collected from indoor air while a single participant was present in the room, and that it is also possible to infer that individual’s behavior. In this study, we investigated whether it is possible to identify an individual even after a certain amount of time has elapsed since that participant left the room.

Materials and methods

This study was conducted in a room used by multiple people. To collect eDNA from the indoor air, a handheld vacuum cleaner equipped with a HEPA filter at the intake port was used. We confirmed in advance that no DNA was adhering to the HEPA filter. A single participant remained in the room for 8 minutes, performing either high-activity or low-activity behaviors. After the participant left the room and a specified amount of time had elapsed, we placed the handheld vacuum cleaner on a table inside the room, and then operated it on strong mode for 8 minutes. Afterward, the HEPA filter was collected for DNA extraction. Subsequently, we amplified 24 human DNA markers and attempted to determine the DNA profiles using electrophoresis.

Results and discussion

In eDNA samples collected within 30 minutes after a single participant who had been moving around actively inside the room had left, although the allele peak height decreased over time, an allele detection rate of over 85% was achieved, making it possible to identify the individual. However, in samples collected at later times, the allele detection rate fell to 50% or less, making it difficult to identify the individual. Furthermore, when the participant’s movements during their stay were minimal, identification was sometimes difficult even with samples collected 5 minutes later. Based on these results, this method is effective to identify the individual present at the time of eDNA collection. Depending on the individual’s behavior, it was considered possible to identify the individual using samples collected up to approximately 30 minutes after the individual left the room.

Authors

• Atsushi Nagai (Gifu University, Japan)
• Shunsuke Yamada (Gifu University, Japan)
• Masaomi Okamoto (Gifu University, Japan)
• Yurika Ushimaru (Gifu University, Japan)
• Yui Goto (Gifu University, Japan)
• Yukiko Dozen (Gifu University, Japan)
• Waka Kobayashi (Gifu University, Japan)
• Yuuna Natsume (Gifu University, Japan)
• Tomomi Michiue (Gifu University, Japan)