AURORA, Colorado: On the afternoon of June 2, Colorado police say, a former teacher named Christian Paetsch walked into a Wells Fargo bank waving a gun and told everyone to lie down.

About 15 minutes later police descended upon a nearby intersection, blockading dozens of shocked motorists - including Paetsch, whom the authorities had tracked with a GPS device buried in $US26,000 he was accused of stealing.

But with only the faintest description and unsure which vehicle the device was in, the police trained their weapons on all 20 cars at the intersection and ordered people to show their hands.

For nearly two hours, police ordered every driver and passenger to step out of their cars, handcuffing some, before finding the money and two firearms in Paetsch's vehicle.

The case, now before the US federal courts, shows that while advanced technology gives police the power to shadow a suspect moments after a crime is committed, there are legal questions over how wide a net the authorities can cast while in pursuit.

At issue is not Paetsch's involvement. Rather, his lawyer, Matthew Belcher,has argued evidence seized from Paetsch's vehicle should be thrown out because the roadblock was unconstitutional.

The Fourth Amendment, Mr Belcher said, should keep the police from rounding up groups of people at gunpoint based merely on a hunch.

Prosecutors argued the roadblock was the safest option, given the potential for a high-speed chase.

They said the tracking device showed the robber was at a specific intersection, and this allowed police to tailor the roadblock.

Last month Judge William Martinez in Denver agreed, ruling the detention of other motorists was justified, given a potentially dangerous criminal was on the loose.

But the judge also said he was troubled by the invasive tactics used by the police towards motorists.

According to the defence, a four-year-old girl wet herself while strapped in her car seat. And a mother was ordered to crawl through a passenger door and then handcuffed in front of her son.