My daughter did her EPQ on law (as was interested in law before she applied for uni for Sept). She focused on criminal law and the age of criminal responsibility and whether children under 10
are able to form a guilty mind (mens rea). It really helped her to discover whether law was of interest and she got to interview a KC (criminal barrister). So I can’t help with your question - but I would encourage you to do a law based EPQ as whilst not all unis recognise the qualification, I think they did like the fact that her PS discussed going to the Old Bailey, law summer school and her discussions/conclusions about the age of criminal responsibility. She got offers from Durham, QMUL and Warwick for law just to put it into context. Good luck!