Police vetting procedure?

[Skoda John]

You do not have to give them the details. They do not have to employ you. Many employers are looking at Social networking sites. There have been several high profile cases of in appropriate posts on social networking sites causing problems. They want to see if you are sensible with your posts and what you have said.
As a police office it is vital you are seen to act in a suitable manor at all times.
I have worked with a guy who was fired over his post on Facebook.