As an aside, I used to drink in The Boot years ago, when I had family living in Weymouth.

Anyway, onto the thread..

My understanding would be that a footprint would indicate some shoes you own, add the red threads from a cardigan that you own and the footprints being heavier on the left side than the right, indicating a back problem.

Any one of these could indicate lots of people. Add them together and Sherlock Holmes would call it elementary. DNA is a bit like that but with many more variables to cut down the likelihood till you are left beyond reasonable doubt that it narrows to one person.

Or I've been reading too many books again.