Sanction Detection Rates

The ‘murder rate’ is one way of measuring the effectiveness of the justice system. Another is the percentage of homicides that are ‘cleared up’ – otherwise known as the Sanction Detection Rate.

This means cases where a suspect has been identified but not necessarily convicted of the crime, perhaps because they have been acquitted on the grounds of self defence. A small number of cases are classed as unresolved, such as the murder of Jill Dando (the suspect was first convicted then acquitted several years later following a retrial).

According to the official definition: ‘A sanctioned detection occurs when (1) a notifiable offence (crime) has been committed and recorded; (2) a suspect has been identified and is aware of the detection; (3) the CPS evidential test is satisfied; (4) the victim has been informed that the offence has been detected, and; (5) the suspect has been charged, reported for summons, or cautioned, been issued With a penalty notice for disorder or the offence has been taken into consideration when an offender is sentenced.’

The Metropolitan Police’s list of homicides for January 2006 to September 2011 (issued in September 2011) revealed that 85.2 per cent of the homicides listed had been ‘detected’. Most are sanction detections but there are a few other detections where the suspect committed suicide after carrying out the killing. This figure can potentially change over time as suspects are charged and put on trial.

Another release under the Freedom of information act breaks down the number of sanction detections made every financial year between 2007/08 and 2010/11.

The Sanction Detection Rate (SDR) is therefore 83 per cent for 2007/08, rising to a consistent 93 to 94 per cent for the following three years.

This is a different kind of measurement because it includes detections of cases that took place in earlier years, and therefore the ‘closure rate’ could potentially be higher than 100 per cent. This sounds absurd (See the debate around the announcement that Washington DC had a 94 per cent closure rate for homicide), but it does give an indication of the effectiveness of homicide investigations. The SDR also does not change over time.

Looking at the UK as a whole, the last set of Home Office statistics gave a sanction detection rate of 86 per cent for 2009/2010 and 83 per cent for 2010/11 (the number of homicides rose from 618 to 642, with the number of sanction detections made over the same period falling from 533 to 530).

Perhaps of more interest is the comparison between the sanction detection rates for homicide and other offences including domestic crime, robbery, burglary, sexual offences, gun crime and knife crime.

Homicide has long been prioritised by the police and the justice system, for obvious reasons. It is investigated centrally by a separate ‘Homicide and Serious Crime Command’ rather than by detectives in the respective borough, and can devote large amounts of manpower and money to analysing CCTV footage, mobile phone data and forensic examination.  There are also far fewer cases to concentrate on compared to other offences – for example in 2009/10, the figures show 117 homicides compared to 51,682 domestic offences, 9,930 sexual offences, 33,479 robberies, 92,807 burglaries, 3,460 offences of gun crime and 12,617 of knife crime.

Clearly, it’s a lot harder to get away with murder.

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