HOUSTON -- Putting a house up for sale may mean giving the keys to your home to a convicted criminal without knowing it, the KPRC Local 2 Troubleshooters reported Thursday.

For anyone who puts a house on the market, copying the front door key is a crucial step. It's a way for realtors to unlock the house to show it to a buyer.

At a locksmith near Katy, a registered sex offender was spotted copying the key to someone's home because he works for the Re-Max Fry Road office. He also carried a master key that can unlock any home on the market in the Houston area, the station reported.

"Ladies are at home and their husbands might be at work, and we're in a very dangerous situation with these people walking around her like that," said Patricia McIntosh, who is selling her home.

McIntosh is fixing up her home, hoping it will sell.

She just found out about the Troubleshooters investigation that showed many other criminals have a key to the lockbox on her front door as well as all the other homes on the market around Houston.

They're called "supra keys."

"It makes me feel very uncomfortable," McIntosh said. "You just assume that if they have that key, then they're OK and they've been checked out, you know?"

But anyone who would check out Robert Casados and others who work with him would find a list of convicted criminals with master keys.

Office owners, called brokers, are not required to check employee backgrounds, so other realty firms may have similar rap sheets.

Court records showed one agent with a 1997 assault conviction, another with a theft from 1993 and a weapons conviction in 1994. Others have drug convictions.

Casados pleaded guilty to sexually assaulting a 14-year-old relative. The Troubleshooters' hidden cameras found him keying into a home, a new listing, where a surprised young mother and her 1-year-old daughter were home alone.

"Turn that camera off," Casados said.

"No, sir," Dean said.

"I'm not talking to you, then," Casados said.

"Well, I think it's an important question, don't you? You have this supra key that gets you into people's houses … ," Dean said.

"I have a ... I understand that I have a job and I'm trying to do my job. That's all I'm trying to do," Casados said.

The man who gave Casados the job, broker Joe Rothchild, isn't talking.

The Houston Association of Realtors said it is against the rules for him to loan his keys out to anyone.

"Need to talk to you about your supra key, sir. Why wouldn't you want to talk about that?" Dean said.

His secretary e-mailed the Troubleshooters later to say that Casados had been fired.

The trade group, Houston Association of Realtors, said there are 19,288 supra keys in circulation.

The only requirement to obtain one is a valid license from the state to handle heating and air conditioning repair or pest control.

The Troubleshooters spotted a pest control worker keying into a home in Kingwood while the family was out. He had pleaded guilty to filing a false police report in 1997

Most of the keys belong to agents licensed by the Texas Real Estate Commission in Austin, where general counsel Loretta Dehay admitted that some murderers and rapists are eligible for licenses under the current rules.

"I would venture a guess that most times we have disapproved their license. I don't have the numbers on that," Dehay said.

"Shouldn't that be a little more absolute? Shouldn't that be an 'always'?" Dean said.

"If we had that flexibility through the law, then we would," Dehay said.

Dehay said the law requires her agency to consider each case. The circumstances of a murder or rape, or letters of recommendation, may mean a convict gets a license.

"But that puts the commission in the position of saying, 'OK, this sexual assault is OK, but that sexual assault is not. This murder is grounds for not getting a license and this murder is not.' Is that the position y'all should be in?" Dean said.

"Because we're required to comply with the law," Dehay said.

"But the law doesn't say that you have to give them a license in some cases. Couldn't you just say, 'All right, murderers don't get licenses?" Dean said.

"We could," Dehay said.

The Troubleshooters found case after case of other felons being licensed.

Court records showed a New Caney agent with a license despite serving time in prison in 1994 for armed robbery and assault with a deadly weapon.

Another Houston agent served time for selling cocaine.

The state insists background checks are done on all applicants. But Dehay admitted the Troubleshooters investigation exposed another loophole. Every two years when an agent renews a license, no one checks for any new crimes.

"There is not a background check done on each renewal. We rely on the licensee to answer a question on the application, the renewal form, that asks if they've ever been convicted of a crime," Dehay said.

That means agents like Clear Lake real estate agent Darren Slawson can simply lie on the form, the station reported.

The Troubleshooters found him carrying a supra key, even though he served 80 days in jail for sexually assaulting a 14-year-old girl. Her dad walked in on them.

Slawson pleaded guilty. One month after beginning his probation in 1999, records show, he answered no for "charges pending" and no for "ever been on probation?"

Police hauled him to jail for what officers said was another scheme to stay in the realty business.

He's charged with failing to register as a sex offender.

"You guys must have a slow news day to be interviewing me," Slawson said.

"You pleaded guilty to a crime and then you got around the sex offender law. Was that just trying to beat the system?" Dean said.

"No, it's just trying to live," Slawson said.

"Giving him access to any house that's for sale in the Houston area would certainly make anybody nervous," said Sgt. Dan Krieger with the League City Police Department.

Because of the Troubleshooters investigation, the Houston Association of Realtors said it would push the state to fix its licensing guidelines.

"We don't want criminals having access to a license, much less a lock-box key," said Bill Jones with the Houston Association of Realtors.