The Sun's headline - "1,200 killed by mental patients" - is inaccurate
This article has now been updated with more information on the quality of these statistics.
Today The Sun's peers on Fleet Street accused the newspaper of running a headline that's "misleading". The headline in question reads "1,200 killed by mental patients" and introduces a two page spread looking at "the disturbing failings in Britain's mental health system".
The source of The Sun's 1,200 figure is a recent report from the University of Manchester. However, one of the academics behind the study has now accused The Sun of misquoting the numbers in their research.
Here's how The Sun arrived at its conclusion that "mental patients" have been responsible for 1,200 deaths over the past decade (2001-2010 data). It appears to be the total (1,216) for the number of victims killed by someone who was either identified as a "patient" at the time of their conviction (which means they'd been in contact with mental health services in the year prior to their offence) or who had presented "an abnormal mental state" when they committed their offence.
In other words, the 1,200 individuals aren't all "mental patients". According to the report, a person experiencing feelings of depression might be described as someone with "an abnormal mental state" - a definition that refers to a range of symptoms "of all severity". The report makes it clear that this group are not patients:
"Most of these people were not under mental health care; therefore most were not preventable by mental health services."
Between 2001 and 2010, around 64% of the homicides committed by those suffering from mental illness involved those who had been (or were at that time) patients of mental health services.
It's worth bearing in mind that there are limitations to these statistics. For instance, only homicides that result in a conviction are recorded and identifying mental illness in so-called "non-patients" is dependent on psychiatrists preparing evidence for court, which doesn't always happen.
We will be contacting The Sun about obtaining a correction to its headline.
UPDATE (9 October 2013)
This article was amended to include information on the limitations of these statistics and in place of "approximately half of homicides" we're using the more accurate figure of "around 64%".