Whichever career you choose, maths is always a good one to have. It makes you more well-rounded and gives you a lot of transferrable skills. Based on the fact that you want to do forensic psychology, in my opinion, either biology or law and criminology or both would be good, depending on which one you like. Word of warning though biology has A LOT of content which can be overwhelming, but obviously, if you enjoy it then there's no reason to not do it. Just depends on you. Hope this helps.