The answers are multifaceted. For one thing, one device found at a crime scene or on a suspect is not the same as DNA found in the same places. Instead, the device contains the digital data comparable to DNA: not just the content, but also the metadata, usage patterns, and even versions that help to determine how data got on a device.
Thus the mathematics in calculating likelihood can get complicated — compounded by the fact that for digital forensics, researchers are still figuring the math.
As a result, said Hannes Spichiger, a Lucerne University of Applied Sciences and Arts lecturer who has researched the topic since 2017, current capabilities haven’t evolved to the point where they can provide likelihood approaches for more than a handful of digital traces.