Society looks to the police to enforce the laws of the land so that rest of us can go above a daily lives safely and free from crime and the fear of crime: for the most part this works. If someone breaks the law police can be called along to confront that person and prosecute them if need be. But the police are expected to do this in an open and fair way because openness and fairness it critical to retaining public confidence.
We do not expect police to spy and try to undermine the very people they should be helping.
Most of the public accept that from time to time police will get things wrong - police officers are only ordinary human beings who come from a society which is far from perfect. Police reflect exactly the society they come from - how could it be otherwise?
The only difference the police and everyone else is some training, a discipline code and a culture, which at its best, means they do their duty in difficult circumstances. But if anyone thinks a few hours training changes officers from ordinary citizens in an imperfect society to people who can address all the problems our society tends to ignore then they are being unrealistic to say the least.
When police get things wrong or do wrong they should be open to complaint and investigation and to public debate because trust in the police is critical to the well-being of society.
But now a number of allegations have been made about police spying on the family and friends of Stephen Lawrence. Allegations have been made about a cover up after the Hillsborough disaster and numerous allegations have been made about undercover officers and what they have done over the years.
A theme has started to emerge which suggests some police officers have sought to undermine the credibility of those with legitimate complaints against police.
In the case of the Stephen Lawrence the police not only failed the Lawrence family by not investigating the murder of their son properly but may have sought to ruin the family's reputation to reduce their credibility as complainants.
In the case of the Hillsborough disaster it seems that police may well have sought to trash the reputation of the victims of police mistakes in order to avoid being held to account for what went wrong.
If these allegations turn out to be true the officers doing these despicable and cynical things should be prosecuted where laws have been broken.
Police gets lots of things wrong - it's a very difficult job - they have to pick up the pieces when the rest of society resorts to hatred and violence and crime. Like the rest of society a small number of police officers are dishonest, some are racist and some are not good at their jobs.
Any improvement in the way this country is policed depends on an honest and open debate and much good can come from it.
It is serious enough if police fail to investigate a major crime or mishandle something which leads to the deaths of innocent people - to then try to damage the reputation of the family and friends or the victims to cover up failings is a dreadful and cynical thing to do and we should not tolerate it.
Public debate and openness does work - I remember what it was like being in the Met Police when the findings of the Stephen Lawrence inquiry came out. It had a very profound effect where I worked. I can't speak for the rest of the Met - but I think it changed the way we thought and acted in relation to different groups in the community in a positive way. We had to try harder and I think we started doing that. Things still need to improve but progress has been made.
But the police spying on the very people they are sworn to protect in order to undermine them is a cynical act and a betrayal of the police service and of societies trust in them.
It is a misuse of police time and those in charge have no authority to do it. It is akin to stealing public money because the tax payers pay for police time and they don't pay for the police to run secret operations to undermine the victims of police mistakes.
Worst still, it makes it more difficult to make improvements to policing in this Country in an open and honest way and it prevents justice being done.