Like every person in this world, we all need security and safety. We can not be too trustful in a person that we have just met for the first time. It is hard to give full trust to an individual especially if that person look too suspicious.

It is not a bad thing to be suspicious, it is like being safe and sure that you won't make any mistake in the end and regret an action that you have committed.
 
If you are a parent who is trying to secure your child life, you won't hire a nanny that has criminal record or even hire a stranger who knocks on your door applying to be a nanny of your child. You need to evaluate applicants before hiring them. Of course interviewing is not enough, you need to have a thorough evaluation to make sure that the nanny that you will hire don't have any criminal records.
 
Conducting background check is the only way that you can do to have a total evaluation of the applicant. In background check, you will know the employment history of the subject. Included on the result of background check is criminal record. So you can easily detect if a person who is applying as nanny is a convict and have bad records.
 
In this way you can protect your child from any harm and secure the life of your family. Conducting background check should be a standard procedure before deciding hiring a person to look on your child while you are away.