If the officer can't do it, then there was no reasonable suspicion and the stop is deemed illegal.
Well, at least that's the way we learned it.
According to the Texas Court of Criminal
In Derichsweiller v. State, No. PD-0176-10, (Tex.Crim.App. 2011), an officer was called out to a Wal-Mart parking lot after a couple in the McDonald's drive-thru called 911 about a man who drove up alongside their car and grinned at them. He drove around the restaurant and stopped and grinned a second time before driving off into the Wal-Mart parking lot.
There were no allegations that Mr. Derichsweiller was doing anything illegal -- just weird. The officer stopped Mr. Derichsweiller while he was circling the Wal-Mart parking lot. The officer didn't witness Mr. Derichsweiller doing anything remotely illegal. Of course after he stopped him, the officer noted a strong odor of alcohol and then commenced a DWI investigation. And Mr. Derichsweiller had two prior DWI convictions.
The trial court found no problem with the stop and denied Mr. Derichsweiller's motion to suppress. The Court of Appeals, on the other hand, had a problem with the stop and reversed the trial court on the grounds that neither the officer, nor the couple at the restaurant, witnessed any behavior that suggested Mr. Derichsweiller was involved in criminal conduct.
The Court of Criminal Appeals disagreed and stated that
[w]hile it is admittedly a close call, the information known collectively to the police in this case ultimately satisfies this standard. The appellant's conduct, particularly as directed at the Holdens, while not overtly criminal in any way, was bizarre to say the least. Moreover, the repetition of similar, apparently scrutinizing, behavior directed at parked cars in the adjacent Wal-Mart parking lot reasonably suggests a potential criminal motive that transcended any particular interest in the Holdens themselves. It reasonably suggests someone who was looking to criminally exploit some vulnerability--a weak or isolated individual to rob or an unattended auto to burgle. It matters not that all of this conduct could be construed as innocent of itself; for purposes of a reasonable-suspicion analysis, it is enough that the totality of the circumstances, viewed objectively and in the aggregate, suggests the realistic possibility of a criminal motive, however amorphous, that was about to be acted upon. Under these circumstances, the Fourth Amendment permits the police to make a brief stop to investigate, if only by their presence to avert an inchoate offense.So now what does "reasonable suspicion" even mean? Does it mean anything? Sure, Mr. Derichsweiller's behavior was bizarre, to say the least, but does it follow that bizarre behavior now gives rise to reasonable suspicion that someone is about to commit a crime?
Reasonable suspicion of what? The facts pointed to no criminal offense. The officer's observations of Mr. Derichsweiller's driving pointed to no criminal offense. It would appear that the court's decision had more to do with finding a way to uphold a felony DWI conviction than upholding the Constitution.