I don't think the problem is with the number of samples. You're not trying to identify the culprit (automatically) among many potential suspects. You're doing w

I don't think the problem is with the number of samples. You're not trying to identify the culprit (automatically) among many potential suspects. You're doing what is basic scientific research: you're using all the data you have to try to _disprove_ that he's that guy - which you can do with near 100% certainty. Any missing feature can clear him. After a certain amount of effort you give up. Which means the trust you have in the team is a lot more important than the size of the dataset. I don't know how checks and balances would look here. Maybe make available each analysis to the defendant and let him/his team check it out? Like another commenter said in this thread, some people were convicted on DNA evidence of a hair that wasn't even human. A larger sample won't fix that.