I intend to contest a ticket for an improper left turn. Do I need legal representation in court or can I represent myself? Should my passengers go with me as witnesses?

Yes you can represent yourself.
You mark "not-guilty" and "officer present" on the back of your ticket, take it to the courthouse and wait for your trial date to arrive in the mail.
The Crown will make its case by calling the officer to the stand and asking him pertinent questions.
Then you get a turn to ask the officer questions.
Then the Crown will rest it's case, and the JP will give you a chance to present your case.
You can then call your passenger as a witness and ask them questions.
BEWARE! The Crown can then ask YOUR witness questions (and they're very good at this game!).
You have the option of then taking the stand and letting the Crown ask you questions, or you can rest your case.
The JP will then call for a closing statement from the Crown. He will resite the facts that prove your guilt.
You will then get a chance to make a closing statement explaining how the Crown hase failed to prove it's case. Have something prepared beforehand. You can read from a prepared statement.

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