(15) Every driver approaching a traffic control signal showing a circular amber indication and facing the indication shall stop his or her vehicle if he or she can do so safely, otherwise he or she may proceed with caution. R.S.O. 1990, c. H.8, s. 144 (15).
(18) Every driver approaching a traffic control signal showing a circular red indication and facing the indication shall stop his or her vehicle and shall not proceed until a green indication is shown. R.S.O. 1990, c. H.8, s. 144 (18).
I guess the officer will say that I was approaching on the red but at some point I was approaching the amber and approaching longer than for the red. I've asked for disclosure to see the measurements and his statement.
If it were me, I wouldn't take it to trial. I would focus my strategy on getting a plea deal with the Crown to a lesser charge (perhaps, Failure to obey sign).
You might find this thread helpful:
If you could have stopped on the Amber then by law you are required to, or if you think you can make it through then continue with caution, while making sure it doesn't turn red before you finish crossing.
I think your best bet here is a plea bargain, as the cop probably saw the whole thing and will testify that he saw you go through a red.