I would say that from what we saw from the lawyers survey, the two things that are most likely to result in acquittal are evidence to the contrary and charter issues. Evidence to the contrary appears to be a rather substantial hurdle in some jurisdictions, like Quebec, and charter issues appear to be substantial hurdles as well. So these are the technicalities you were talking about.
There are a lot of things being done. For example, in California the roadside breath test is actually an evidential test. So that precludes the officer from having to go back to the station to do yet another test that would be admissible in court. They do it roadside, and it's admissible in court. There are automated paperwork systems. There are several things that can be done and that some jurisdictions are looking at to speed up the process and make it easier to arrest and overcome all the hurdles. But generally what you'll see is that there are going to be challenges: they didn't have reasonable probable cause; they didn't have proper grounds for making an arrest.
The charter issues that are the biggest problem are section 8, section 9, and paragraph 10(b); that's search and seizure, arbitrary detention, and retain and instruct counsel. Retain and instruct counsel is the biggest charter issue facing lawyers in impaired driving cases.