Digital traces and physical activities: opportunities, challenges and pitfalls

The strong integration of consumer electronics in everyday life offers many new investigative opportunities. In particular, digital traces from smartphones, smartwatches and activity trackers can now increasingly be used to infer information about actions performed by their users in the physical world that might not be obtainable from any other types of forensic evidence. While potentially very valuable from an investigative perspective, making forensically justifiable statements about such traces can sometimes be more difficult than expected. Requirements for this have not yet received much attention in the digital forensic literature. To help filling this gap, we describe the principles we use in determining the evidential value of such traces, which emphasize the need for experimental verification. For such research, aimed at determining the evidential value of these traces, we coin the term data2activity. In this paper, we devote attention to the potential and limitations of data2activity traces, focusing on challenges and giving two examples to illustrate potential pitfalls in interpreting data. Finally, future research directions into data2activity traces are indicated that, in our opinion, should be given attention. These include development of future-proof data acquisition and storage methodology, enabling division-of-effort and sharing of information, as well as development of labeling methodology for free-living experiments.