My 17 year old son gets pulled over for driving too slow in an ice storm in Winnipeg FEb 09 and ends up in jail. They do a urine test for THC and find traces of the chemical. They let him go and don't say anything about charges and 4 months later they want to charge him with a DUI. Can they charge u so much later and not advise you your rights when being tested? I feel if there were to be charges, they should have been laid back in February, right? The RCMP say there have been attempts to serve my son but there is no evidence to prove they tried to serve him. Then the RCMP give us one week to be in court. Just seems so unreal they can treat you like this.
Thanks

You will want to find a lawyer.

They can charge him whenever they choose as long as it is within the statute of limitations. In most parts of the US, that's 1-2 years.