What is a unconstitutional lineup

This is a difficult question to answer because I feel like you are asking about two completely different things, i.e., a Police Lineup vs. a Police Show Up. In your case it sounds like they drove the complainants by in the police cruiser to say do you see the guy who allegedly did this. These can be inherently suggestive (as you've pointed out). Please review Stovall v. Denno, 388 U.S. 293 (1967) to learn more. You can google it. You should also google and read Constitutional Ramifications of the Police Lineup.

Sounds rather improper to say the least, there are, or should be, strict protocols in place to minimize the chances of a false identification when police are presenting your image to a crime victim, taking the alleged victim by your house where you are probably already in cuffs is not part of that process...Missouri allows mechanisms by which this "line up" can be challenged in court. I have seen judges throw out Improper out of court id's in the last. Contact an attorney soon.

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