Recently, a nanny in Los Angeles was accused of dumping the children she cared for at an unlicensed day care so she could go sell produce. Eventually, something felt amiss and the parents of the twin girls began to investigate. Five families have been named in the misdemeanor case against the nanny -- each family had placed two children in her care, including the twins. Authorities said they believe up to 30 children could be involved, and the investigation is continuing.

One family said they trusted her and felt like she was a member of the family. But how well did they really know her? We asked "The Nanny Doctor," Lindsay Heller, a licensed Clinical Psychologist who provides consultation services to families and their nannies, to weigh in on ways something like this can be prevented. Dr. Heller believes that being diligent and using "layers of safety" is key:

1) Check Resume: Your potential nanny should be able to show you a resume of her work history. Be aware of gaps in unemployment and be sure to ask why there were periods she was unemployed. Also, make sure your nanny has had experience caring for children the same age as your child.

2) Check References: Sometimes parents skip this because they fall in love with a candidate. However, you need to make sure that the families they've worked for are real, that the ages are real and the dates that she worked match up.

3) Background Check: This is very important and many parents skip this process. It costs about $50 for a service to run the check; you can pay extra to check to see if they are listed in the sex offenders registry. You should also have your nanny provide you with a driving record from the DMV. The record dates 10 years back and will include any history of moving violations, DUIs, etc.

4) Nanny Cams: If you use them, it's important to be up front with your nanny. A professional nanny would not have any reason to be concerned. A nanny cam is used to prevent something from happening, not for catching it.

6) Have a Trial Period: Not every family can afford or have the time for this, but if you think you've found "the one," commit to spending at least one day training her and helping her to transition in to your home.  Some transitions can take weeks or months.

7) Pop In: If you can't pop in unexpectedly to see your nanny at home with your children, then enlist a friend or relative to help.  In the first few weeks or months, it's important to see your nanny in action.

8) Listen to your Mommy Sense: If your gut tells you that something is wrong, listen to it! Talk to another parent who has a nanny or who has been in a similar situation and have them weigh in. Never ignore yourself if you think something is just not right.

9) Hire a "Connected" Nanny: It is a good sign when a nanny is connected to other nannies in the community. They are -- in essence -- a part of your routine (daily walks, trips to the park, etc.) and are able to observe your children with your nanny.

10) Designated Destinations: Whether it's nearby park, or a trip to the zoo, you should always provide your nanny with a list of approved outings and know exactly how your child will be spending their day. Your nanny should not have carte blanche to just pack the car up and head out for the day. This can be a very dangerous approach.

Here are few red flag/warning signs to look out for:

• Poor Communication: If you repeatedly have trouble reaching your nanny on the phone, or she doesn't check in with you as much as you'd like, this is definitely something to be aware of.
• Oppositional Behavior: If there are times when you tell your nanny you want something to be done and you see a persistent disregard or defiance, this may be a red flag.
• Change in Child's Behavior: If the child is scared of the nanny or saying things that aren't making sense or adding up, this is definitely a case that needs to be investigated further.

See Also:

• Is This Nanny Ad for Real?
• Why Nannies Suck
• Playmates Double As Family Nanny?
• My One-Year-Old is NOT 'Sexy'