Yes, the tape can be used against you in court.
California law prohibits taping of CONFIDENTIAL conversations without the consent of all parties involved. A reasonable person would not believe a conversation with a police officer, who is taking a report, would be confidential.
If you are questioned by the police, here is the ONLY thing you should say: "Officer, I respectfully decline to speak with you. I wish to remain silent and have a lawyer present if you're going to ask any more questions.
Please understand that this is a general discussion of legal principles by a California lawyer and does not create an attorney/client relationship. It's impossible to give detailed, accurate advice based on a few sentences on a website (and you shouldn't provide too much specific information about your legal matter on a public forum like this site, anyway). You should always seek advice from an attorney licensed in your jurisdiction who can give you an informed opinion after reviewing all of the relevant information.