In the years since the Sept. 11 terror attacks, the FBI has used similar snares to catch suspected terrorists.

A 2010 FBI operation in Catonsville led to the arrest of Antonio Martinez, who authorities said agreed to blow up a military recruiting center using a car bomb supplied by undercover agents.

Retired Alabama Judge Joseph A. Colquitt, who has studied entrapment standards, said law enforcement officials must carefully balance public safety and civil rights.

"Aggressive operations by police protect the public and prevent crime," Colquitt said. "Sometimes, though, the entrapment doctrine fails to protect otherwise innocent actors from being drawn into criminal activity."

Veteran ATF Agent Richard Zayas, testifying in cases in Maryland and Arizona, has said the agency honed its operations over time to ensnare drug-robbery crews and minimize risks to the public.

When the ATF began running the operations back in the 1990s, Zayas said, agents sometimes would conduct surveillance on crews and try to arrest the targets before they carried out a real robbery, only to come away without enough evidence to press serious charges.

Later, the authorities would lure suspected robbery crews to a house owned by the government and stocked with real drugs. But that sometimes led to shootouts, Zayas said, as crews confronted armed agents.

Eventually, the ATF hit upon the idea of describing a robbery at an undisclosed location but making the arrests at a separate meeting point. Now the operations by both the ATF and DEA are structured in the same way, court filings show.

Special Agent Edward Marcinko, a DEA spokesman, said the agency has the technology to remotely disable specially wired vehicles to prevent any getaway attempts.

Wallner, the prosecutor in the hotel robbery case, wrote in court filings that the current strategy is "universally accepted."

"The script utilized by law enforcement in this case, and perfected over time, is nearly identical to the scripts used in dozens of other similar cases throughout the country," he wrote.

While authorities say the stings are now designed to minimize danger, the new tactics don't always end in peaceful arrests.

Two ATF-led robbery stings in Baltimore erupted in gunfire last year. In one incident in Hampden, authorities say a suspect attempted to run down an officer as federal agents closed in. He was shot as a quick-response team threw stun grenades to disorient others.

The hotel robbery setup, like other stings, began when an informant approached a group of people suspected of being involved in drug robberies and explained that he felt slighted by his superiors.

Authorities say the informant complained to the suspects that he had been overcharged for drugs — then suggested they help him with a robbery to get even.

The targets were eager to get involved in the robbery, according to charging documents.

"This [stuff] right here … this make my day … this my line of work," Michael Johnson, one of the crew's members, said in a conversation summarized in court filings.

Johnson has pleaded guilty to a robbery conspiracy charge and faces 15 years in prison. Johnson had a criminal history, but his attorney questioned whether investigators were really catching only the most serious offenders.

"They could go into any neighborhood and make this type of offer, and you'll get guys to jump at it," attorney Christopher Purpura said after the hearing. "I don't know they're getting the worst of the worst."

Rodney Proctor also pleaded guilty to robbery conspiracy and gun charges. He faces up to 12 years. The remaining defendants are fighting the charges.