What are u talking about?? I assume you're not currently working as a lawyer, well I really hope not.

Get some legal advice, go for legal aid or a private lawyer. You can get off, but it might cost you. The police officer is regarded as a credible witness so the judge will take his version of events as gospel (generally) and it's then up to u or your lawyer to find various holes in his story like how dark was it, how far away were you etc etc.