The so-called Sarah's Law, which permits parents to ask the police if someone with regular, unsupervised access to their children has a record for child sex offences, is being rolled out to eight further police force areas in England following a trial in four. What kinds of scenarios could the scheme cover?

The new boyfriend

A single mother meets a man who she likes but is worried that she does not know enough about his background to allow him fully into her family's life. She telephones the local police and requests information about the man.

If the mother is given the information, she will be asked to keep it confidential - and could face civil or criminal action if she does no

The police will check the background of the man because the request has come from a mother - someone who is directly responsible for children. Officers will carry out two checks - a priority check within 24 hours, followed by a more thorough risk assessment which takes longer because it will delve into someone's history.

If there is a criminal record, the pilot constabularies say they would use special child protection measures, jointly run by police and probation officers, to work out how best to deal with the suspect.

If there is a serious risk, police may also pass on some of this information to the mother - but only if they are convinced that it is necessary and proportionate to protect the children.

If the mother is given the information, she will be asked to keep it confidential - and could face civil or criminal action if she does not.

If the investigation does not find any record of sexual offences, but does find other worrying behaviour, such as a conviction for domestic violence or intelligence of worrying behaviour, the mother may still be given information to help her protect her family.

New boyfriend worries others in family

A couple are concerned that their daughter's new boyfriend is not trustworthy and they are worried about their grandchildren.

Like anyone else, the grandparents can already alert the police.

Police stress they would always check out the concerns of other family members or friends as part of standard child protection measures.

However, the grandparents are not directly responsible for the welfare of the children and any relevant information which would be released under the scheme would go only to the person with direct responsibility for the children - in this case the mother.

The neighbour playing with children

A family are suspicious of a neighbour's intentions towards local children. Police will, as ever, make checks. But they will release information of concern to parents only if the individual has direct access to their children.

In other words, if the family who alert the police have nothing to do with the neighbour, they will not know the outcome of their inquiry - but other parents whose children are more directly involved with the subject may be given information.

Police may have a difficult judgement to make if someone is asking about a neighbour, who officers know is an offender but have no reason to suspect poses a risk because he is co-operating with monitoring arrangements.

The odd-looking neighbour

A family doesn't like the look of the man who lives nearby. They say he's a bit shifty, reclusive and is always rude if spoken to. They ask the police to tell them about the individual's background.

Police are highly unlikely to provide any information because the family has not provided any reasonable suspicion that children are at risk.

The pilot's purpose is to protect children and the family will have to show that the neighbour has some kind of access to their children. One concern over the pilots is that they could be used to settle scores and spread malicious rumours. This block on unwarranted requests for information, and the insistence on confidentiality, is designed to prevent rumours spreading.

The sports coach

A man has been offering informal football coaching and doesn't seem to be part of any club, leisure centre or school set-up. A parent is concerned about rumours about the man doing the rounds.

Parents can ask for information because this is clearly direct access to their child. If the coach is found to be a risk, the parent will be told but will also be asked to keep that information to themselves.

The full force of multi-agency monitoring arrangements will come into action to stop the man. The success of these monitoring arrangements relies greatly on preventing someone going underground. A local witch-hunt or vigilante action increases the risk of someone disappearing from view.

Some child protection experts predict these kinds of scenarios will be the hardest to manage because a parent who has information on the man's record may feel overwhelmingly obliged to alert others, regardless of police warnings.

If the man poses no risk and has simply been a little naive, police may advise him how to avoid any future misunderstandings, such as by ensuring that he can provide an up-to-date criminal record check.