A specialist on the psychology of crime and the development of criminal behaviour has joined the University of Greenwich as its new Professor of Criminology. Darrick Jolliffe is the author and co-author of numerous articles, book chapters and reports on the two areas of expertise. He is also an expert on evaluating whether 'interventions' can help reduce reoffending. His work has assessed the impact of community justice initiatives, high-intensity training for young offenders and methods of policing violence by organised gangs. He is also a lead independent evaluator of the Social Impact Bond at Peterborough Jail, the first 'payment by results' scheme for reoffending in the world.

Formerly a senior lecturer in criminology at the University of Leicester, Professor Jolliffe said: "I am looking forward to being part of the dynamic and enthusiastic team at Greenwich. The university already has a fine reputation for teaching and my ambition is to contribute to the existing upward trend that criminology at Greenwich has for research excellence."

Greater Manchester Police are reported to have apologised to a gay man who was forced to give a DNA sample for a national database under new powers for investigating 'historical' crimes.

The 50-year-old former soldier said the sample was taken because of a conviction 30 years ago for having consensual sex with another man, despite the fact the law under which he was convicted no longer applies.

The incident is one of a number of instances where police have been accused of demanding DNA from gay people convicted of offences decades ago under legislation which has been abandoned. They are part of Operation Nutmeg, being carried out by forces across the country following the introduction of the Crime and Security Act, which became law last year.

Figures published by the BBC under the Freedom of Information Act show that 653 people were charged in 2012 for alleged offences carried out on social media sites – out of a total of 4,908 offences reported to 29 forces in England, Scotland and Wales. That compares with figures of 46 out of 556 in 2008.

The revelations come in the wake of publication by the Director of Public Prosecutions Keir Starmer QC (pictured) of interim guidelines setting out the approach prosecutors should take in cases involving communications sent via social media. The guidelines are designed to give clear advice to prosecutors and ensure a consistency of approach across the CPS to these types of cases.

Mr Starmer said: "These interim guidelines are intended to strike the right balance between freedom of expression and the need to uphold the criminal law. They make a clear distinction between communications which amount to credible threats of violence, a targeted campaign of harassment against an individual or which breach court orders on the one hand; and other communications sent by social media, such as those that are grossly offensive, on the other.

The Sentencing Council for England and Wales is consulting on proposals for how guidance for courts on sexual offences should be brought up to date. It aims to give more focus to the impact on victims and reflect advances in technology, while making sure offenders are dealt with effectively.

Its draft sentencing guideline, which covers offences such as rape, child sex offences, indecent images of children, trafficking and voyeurism, proposes a variety of changes to how offending is dealt with by the courts.

The council believes that as well as physical harm, the psychological and longer term effects on the victim should be more fully reflected. Factors such as stalking and previous abuse, including violence, can make the victim more vulnerable to harm and are set out as factors that can be taken into account.