Here's the proper case law. It's binding on lower (traffic courts)...
PS I thought it was R. v. Winslow, but it was R. v. Wannamaker...this is why you pay your 15 overs...
R. v. Wanamaker
Her Majesty the Queen, and
 O.J. No. 1581
Ontario Court of Justice
Y. Renaud J.
Oral judgment: January 25, 2005.
Criminal law — Appeals — Procedure — Information or indictment — Amendment — Transportation law — Motor vehicles — Offences — Speeding.
Appeal by Wanamaker from his conviction for speeding. Wanamaker was clocked traveling 113 km/h in an 80 km/h zone. The officer exercised his discretion to issue a ticket for traveling at 100 km/h. At trial, the judge granted the Crown leave to amend its certificate to allege that Wanakamer traveled at the speed at which he was clocked. Wanamaker was informed of the proposed amendment prior to trial and elected to proceed with his defence, notwithstanding the amendment. Wanamaker was convicted. He appealed on the basis that he would have paid the ticket as originally prepared had he known that he faced a higher penalty under the increased speed.
HELD: Appeal dismissed. Wanamaker was aware of the amendment and could have either entered a plea to the offence prior to the amendment, or sought an adjournment. Wanamaker chose to proceed and was thus precluded from arguing that he was treated unjustly or prejudiced in the course of his defence. Statutes, Regulations and Rules Cited:
Provincial Offences Act, s. 34.
F. Perron, for the prosecution/respondent
M. Grossi, for the defendatemnt/appellant
REASONS FOR JUDGMENT
¶ 1 Y. RENAUD J. (orally):— The defendant appeals his conviction for speeding, specifically that he travelled at one hundred and thirteen kilometres an hour in an eighty kilometre per hour zone.
¶ 2 The evidence indicates that the defendant was told by the officer, who pulled him over, that he was travelling at one hundred and thirteen kilometres per hour. The officer exercised some discretion and prepared the Certificate of Offence charging the defendant with speeding at the rate of one hundred kilometres per hour in an eighty kilometre per hour zone.
¶ 3 At the commencement of the proceedings on the day of trial, prior to the defendant having been arraigned, the prosecution advised the court that it would, during the course of trial, be seeking an amendment to the Certificate of Offence by increasing the alleged speed from one hundred kilometres per hour to one hundred and thirteen kilometres per hour. The defendant, who was present on the day of trial and represented by an agent, entered a plea of not guilty and proceeded with the trial.
¶ 4 Later on in the proceedings, just as the prosecution had advised to begin with, the prosecution sought the amendment to the alleged speed. The trial court heard argument on the requested amendment and determined that it was proper to grant the amendment to accord with the evidence received.
¶ 5 Though the trial justice does not so expressly state, it is sufficiently apparent from his reasons that the court took into account the important fact that the defendant had been alerted, prior to his plea, that the prosecution was intending to seek the amendment in question. The presiding justice noted that the defendant conducted his defence notwithstanding the expectation that the prosecution would be seeking the amendment.
¶ 6 The considerations that guide the trial court in deciding whether to grant an amendment to an information or certificate are stated in s. 34 of the Provincial Offences Act. The trial justice was obviously aware of these considerations since submissions were made to the court on this point.
¶ 7 Pursuant to the section, the question whether or not to grant the amendment is a question of law.
¶ 8 On this appeal, as well as at the trial itself, the agent for the defendant submits that had the defendant known that he would be facing a higher penalty, given the increased speed alleged, the defendant may well have opted to pay the ticket as originally prepared. One might also concede that if the defendant had known that the charge to be tried was more serious (given the increased speed being alleged), was more serious than that which was stated on the Certificate of Offence, different or greater efforts would have been made to defend the charge.
¶ 9 The difficulty for the appellant in this case is that the prosecution did inform the court, and in so doing alerted the defendant, that an amendment would be sought. It would have been open for the defendant, had he felt prejudiced or unjustly treated by this request, to ask for an adjournment to further consider his options, or indeed, to enter a plea to the certificate as it then read, prior to the amendment being granted. The defendant did neither and chose to proceed with the trial.
¶ 10 The court has.considered the case of R. v. Antunes,  O.J. No. 4898, a decision of Justice Halikowski. In that case the trial court had granted the amendment, increasing the alleged speed of the defendant's vehicle, this amendment having been granted at the end of the trial, after the plea had been entered and after the evidence had been taken, without the defendant having been informed prior to the commencement of the trial that the amendment would be sought. Indeed, the defendant had not appeared at trial and was represented by an agent. The defendant called no evidence.
¶ 11 On appeal, the court rejected the appellant's argument that the amendment at the conclusion of the Crown's case ought not have been granted and that the amendment was prejudicial or unjust to the appellant. Justice Halikowski was not of the view that in the case before him the increased speed stated in the certificate would have influenced the line of defence and determined that the amendment caused the defendant no prejudice, citing the case of R. v. Irwin (1998), 38 O.R. (3d) 689, at page 698 where Justice Doherty emphasized that the accused cannot be found to have been prejudiced where he has had a full opportunity to meet the issues and where the conduct of the defence would have been the same, even if the amendment had not been made or if the charge had been earlier amended.
¶ 12 Each case, where an amendment is sought, turns on its own facts. In the present case, the court is not concerned with a situation where the unannounced amendment is sought at the conclusion of the Crown's case or at the conclusion of trial. In my view, granting an amendment, without forewarning to the defendant at the conclusion of trial, would more readily support an argument of injustice or prejudice. The court might offer that it would be more helpful if the prosecution were to have advised the defendant well before the trial date of its intention to seek the requested amendment to accord with the anticipated evidence of the officer. This would remove any possibility of inconvenience or additional delay or cost to the defendant, which may otherwise result from the amendment request being announced on the day of trial. This, I would consider, to be a counsel of perfection and not a consideration that would provide necessary merit for a successful appeal in the present case.
¶ 13 I am not called upon to support or depart from the reasoning of Justice Halikowski in Antunes. In the present case, the defendant knew, prior to the commencement of the trial, that the amendment would be sought. It would have been entirely open to the defendant to request an adjournment rather than risk proceeding to trial on the certificate that would inevitably be amended to accord with the evidence.
¶ 14 The defendant chose to proceed. He cannot now successfully complain that he was prejudiced in his defence or treated unjustly.
¶ 15 The appeal is dismissed.
Y. RENAUD J.