There's something called the Bar Mock Trial, which is what it says on the tin - a mock trial. Your school may know about it or someone in your local area will likely be a coordinator, so taking part in that will give you the chance to take part in a 'trial' and assume a role in the legal profession which will give you a lot to talk about in your personal statement.
Also, I believe anyone can go and watch a court case in a Magistrates' or Crown court given there is a public gallery. So going to see any kind of case unfold will show your interest and give you more to talk about. Also, any extra curricula's your school might have, some kind of debating or ethical discussion? That can help with law too.