Agreed. Why would they arrest if they new they would not get a conviction. Sounds like a false arrest.
I think Maryland laws are intentionally vague because it gives the defense lawyers (some of whom participated in writing the laws) something to argue about.
XD40,
Keep in mind the difference between reasonable suspicion (the standard for a terry stop or a traffic stop), probably cause (the standard for an arrest), and "beyond a reasonable doubt" (the standard for a criminal conviction).
Of course, civil cases require only a preponderance of the evidence (or 51%)
Many arrests are made at roadside with probable cause, but in court the judge, or jury, isn't convinced beyond a reasonable doubt.
Police don't (or shouldn't) care what happens in court. Its not our job to try and second guess what will happen in court. If the standard for an arrest is met, many err on the side of caution, make the arrest, and leave it to the District Court Commissioners Office and the State's Attorney's Office to do their jobs.