CBS2 Investigates: How Much Do You Know About Your Nanny?

NEW YORK (CBSNewYork) -- Many people consider their nanny to be a part of their family, but they may not really know the person they've brought home to watch their kids.

"I thought she was a lovely, wonderful person," one mother said.

After being threatened by the nanny she was about to hire, the mother of two is afraid to show her face.

"I didn't know what she was capable of," the woman told CBS2's Hazel Sanchez.

Nannies have been accused of kidnapping, robbery, extortion, forgery, identity theft, and worse.

"You assume that because they care for children they are good people," she said.

A background check showed the nanny -- who she found through a recommendation -- was actually a felon.

"She's been convicted of having an illegal firearm," she said.

Holly Flanders, who runs a nanny consulting service, said a growing number of unsavory characters -- hoping to capitalize on the immediate and growing need for childcare -- are passing themselves off as Mary Poppins.

"Nannies have started to create fake profiles of moms. They use stock photos from Google and recommend themselves as a nanny," she explained.

In reality, they could have a rap sheet as long as your arm.

"There's a lot of people out there who can sit for an interview, and say all the things you want to hear," private investigator Lenny Golino said.

Golino said a complete background check including criminal, financial, and driving records is imperative.

"Are there any summonses, any accidents, DWIs? That's a make-up of the whole picture," he said.

Thomas Ruskin's firm will even spy on your nanny.

"We have seen nannies leave the children outside while going shopping," he said.

Most commonly Ruskin's 'nanny spies' come across things he calls 'nanny distraction' like being on the phone or talking to other nannies when they should be watching your kids.

"That's not what you pay a nanny to do," he said.

Flanders highly recommends employing devices like a nanny cam, and a GPS tracker that attaches to a stroller. They may seem invasive, but they are legal ways of keeping tabs on the whereabouts of your baby.

Flanders said you should tell your nanny about the devices, and also give him or her a list of your childcare expectations.

"What your preferences are for outdoor time, how far your nanny can go, would you prefer her to walk or take a cab," Flanders said.

Flanders said there are plenty of qualified nannies out there, you just need to do your due diligence finding them.

It should also be noted that, according to the Department of Justice, babysitters account for approximately four percent of crimes committed against children, a rate below that of strangers.