POSTING messages on Facebook or Twitter to encourage crime and disorder is just like throwing a brick through a shop window, Chester police have warned.

Detective Sergeant Andy Dodd said: “In both cases there will be repercussions. In the case of the message you are simply using a virtual brick."

DS Dodd leads the Cheshire Police eForensics Department which includes the Hi-Tech Crime Unit.

Monitoring and capturing material which has been put on the social network sites such as Facebook and Twitter is a rapidly growing area of the unit's work.

DS Dodd said: “The social networks have become part of everyday life. It would be ridiculous for police officers to ignore that fact.

“When there are messages and pictures which provide evidence for criminal investigations we have equipment and specially-trained officers to recover them.”

Detective Constables Peter Lee and Dan Parry were involved in recent successful investigations into cases of people using the social networks to incite rioting.

DC Lee said: “In this type of inquiry our first stage is the ‘live capture’ of any messages. In most cases we have usually had a call from a member of the public to say that something has appeared on a Facebook site or as a Tweet or something similar and they are concerned about it.

“Then we have to move quickly. We need to get an image of the message or picture before it disappears from the server. We can search an area of the social network using key words and see what is there.”

The next stage is the seizure of the computer which originated the message. Then the unit can begin what it terms the ‘dead box’ investigation. This can take days, weeks or months.

The computer's hard drive is put in a machine which produces a forensic-quality copy. All future work is done on the copy, with the original data kept exactly as it was.

DC Parry said: “A lot of the messages we are interested in have gone straight to the social network site server, but we can recover fragments, snippets, which have gone on to the hard drive of the computer. We can often build a very complete picture of what has been going on.

DC Lee added: “Now social networking is an important area of life for many people they use it for communicating all types of information. A murderer may use an instant chat message to discuss his plan with someone. He may then go on to the internet to research methods of killing; to buy a gun; to look for ways of covering his tracks; to deter a forensic investigation. All this activity is traceable.

“Eighty per cent of our work is investigating child pornography. Again, the social network sites are becoming increasingly involved. In many cases of that type we provide all the evidence. In other cases we secure supporting evidence in what may be a much more widely based investigation.”