TAMPA, Fla. - Hearing impaired people tuning in to a news conference last week about the arrest of a suspected serial killer in southeast Seminole Heights got a message of gibberish as they watched an American Sign Language interpreter.

Derlyn Roberts, 53, stood to Chief Brian Dugan's right during the Nov. 28 news conference. She was supposed to be providing sign-language interpretation.

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In fact, after hearing from people who complained her signing was inaccurate, officials are still trying to figure out what she was doing there.

People who relied on Roberts for important updates on the Seminole Heights killings, say her translation was garbled and sometimes completely inaccurate.

“From what I understand, she knows enough about sign language that she was able to fake it. But it was not accurate, and it was not clear, and that's a disservice to the deaf community,” said Tampa Police Department spokesperson Steve Hegarty.

It turns out, Roberts wasn't hired by TPD.

Roberts apparently heard about the news conference and showed up at their door that night to offer her services. Hegarty said he gratefully accepted and allowed her in.

Only after fielding criticism did TPD find out Roberts has a criminal record. It dates back to 2005 for charges, including organized fraud and false imprisonment. She also has a long list of aliases.

Hegarty said they’re looking into allegations that she’s done the same thing to others.

“She has shown up at some funerals and things like that around town in the past and done some signing,” he said.

Hegarty apologized and pointed out the next day the department was back to using Purple, a certified and vetted sign language translation service.

Julie Church, Executive Director at the Family Center on Deafness in Largo, said it's an ongoing and potentially dangerous problem.

“If they don't do their job, or the information is inaccurate, then it can be worse than not having an interpreter at all,” Church said.

In 2013, a fake sign-language interpreter marred the memorial service for former South African President Nelson Mandela.

In September 2017, Manatee County brought in a sign-language interpreter who, instead of informing deaf viewers about Hurricane Irma, mistakenly warned the public about “pizza” and a “bear monster.”

“In Florida, you have to have a license to get your nails done, you have to have a license to get a massage,” Church said. “But, to serve in these critical situations where information is important, anyone can walk in and say 'I'm an interpreter.'”

Church and others have asked state lawmakers for years to pass a law requiring sign-language interpreters to receive certification.

Currently, there are 13 states with laws in place requiring interpreters to hold state licenses. Florida is not one of them.

Tampa police vow the same thing won't happen again.

Hegarty said Roberts likely will not face criminal charges because the department did not vet her credentials.

“I don't know if she was trying to be helpful and just didn't do a good job," Hegarty said. "I don't know if she was trying to put something over on somebody. I have no idea."

Editor's Note: Information from the Tampa Bay Times and the Associated Press was used in this story.