Thanks for the info and sorry for the delay.
First off, if the Crown is seeking 90 days jail, I would strongly recommend retaining a lawyer. If you do not have the funds, you can apply to Legal Aid Ontario for a Legal Aid certificate. Call ***-***-**** to apply for Legal Aid. If you are denied Legal Aid, the next best step is to search for a lawyer on the Justice Net's website, which is a site that lists lawyers names who are willing to take on cases at discounted rates: http://www.justicenet.ca
The Crown position of 90 days seems quite extreme, unless you have a criminal history. Either way, any criminal case is "serious" and you should treat is as such, especially if the Crown is taking a position of jail if you're found guilty.
The importance of getting a lawyer in this case cannot be overstated- the legal issues, or at least potential legal issues, will likely revolve around whether one or more of your Charter (Constitutional) rights were violated during the course of the investigation. You hit the nail on the head with respect to one of those rights, which is your right to be free from unreasonable search and seizures (s. 8 of the Charter). All warrantless searches are presumed to be unreasonable, and it would be up to the Crown to demonstrate that the search was authorized by law, if the case went to trial and you filed a Charter application. A lawyer would be able to review your disclosure and determine the potential strength of this argument.
Another Charter issue is whether you were arbitrarily detained, violating s. 9 of the Charter. The police need grounds to stop you and conduct an investigative detention; they cannot do so arbitrarily or randomly. If the police stopped you and investigated you without such grounds, there may be a s.9 violation.
If a lawyer feels that there were Charter violations, they can do one of two things:
1) Bring these arguments up to the Crown in the pre-trial process, with the hope that the Crown offers you a favourable resolution, without the need for a trial
2) Bring these arguments up formally in court at a trial, and ask the Judge to exclude the evidence (ie, the fake ID), as a result of the violations.
I hope this helps. Please provide a positive rating if it has, and good luck with the case.