I am curious if HN has input on this: The court heard the father-of-one downloaded the video two weeks after the massacre in March 2019, but had last viewed th

I am curious if HN has input on this: The court heard the father-of-one downloaded the video two weeks after the massacre in March 2019, but had last viewed the video in April this year, prompting police to search his property. How would they know if/when the video was watched?