question about surveillance camera?! please read and respond please

So I just got a new car and it passed inspection.. nothing wrong with it. I got it from a private dealer. So.. my sisters ex last night saw my car (which he's never seen before as it's new) and kept circling around her apartment and the next morning... my check engine light came on. 

I'm wondering if I buy a surveillance camera and face it at my new car if I can use it in court to prove he did something to my car. I am almost 100 percent sure but need proof.. if they can prove it why can't I use it? My mom said she's almost sure even if we got it on tape we can't use it against him. I have NO money for a lawyer Hence why I had to take a student loan out to pay for new used car