My question involves a traffic ticket from the state of: CA

I was cited for an unsafe lane change CVC 21658(a). I have three questions.

1. Can I subpoena the officer's eye exams from the last five years and if so, how? Is an allowance made for the officer's privacy?
2. How long does one have to be in a lane before he is required to signal to get out of it?
3. Is an unsafe lane change always about not signalling or is there something I'm missing. The statute isn't clear to me.

Thanks!