Rape conviction rates: Ministry of Justice moves to tackle "misleading" measurement

18 May 2011

Earlier, we looked at possible problems with the claim that there is a 6 per cent conviction rate for rape, widely made in the wake of Ken Clarke's comments today.
The concerns raised by the Stern review about the possible flaws with this figure have been taken on board by the Ministry of Justice (MoJ).

In a recent consultation, the MoJ acknowledge the problems caused by different ways of measuring the rape conviction rate. Four different ways of measuring things all referred to as a 'conviction' rate were identified. These were:

a) Convictions for rape and recorded crime
b) Convictions for rape and people prosecuted
c) Convictions for any offence and people prosecuted
d) Convictions for rape and charges heard by jury"

The first of these, which produces the 6 per cent figure, though widely used is described as useful but "misleading in terms of presenting evidence on convictions for rape," by the Ministry of Justice. The Consultation document explains that in future where used it should be referred to as a 'conviction to crime ratio' rather than a conviction rate.

The second measure the MoJ now also refers to as a conviction ratio. This is because offenders convicted in a reporting year are not always the same people who were prosecuted in that year as investigations and trials span more than one reporting year. Thus, consultation explains, it would be misleading to refer to this as the conviction rate.

The third possible measure is one raised by Baroness Stern, a more inclusive measure that would cover instances of 'downgrading', for example if someone was prosecuted for rape but convicted of sexual assault.

The fourth possible measure would be to measure the number of convictions against charges of rape heard by a jury following a 'not guilty' plea, rather than the number of people prosecuted. This measure is intend to better reflect cases where a person faces multiple charges of rape.

To tackle the problem the MoJ proposed in the consultation to to use two conviction rate measures that could also be applied to all crimes. These measures were:

1. The number of people prosecuted for Offence A that are convicted of Offence A and what percentage of all prosecutions for Offence A this comprises: the 'within offence' conviction rate;

2. The number of people prosecuted for Offence A that are convicted of any criminal offence and what percentage of all prosecutions for Offence A, this comprises: the 'all offence' conviction rate.

The consultation asked respondents if they agreed with this new approach, and 88 per cent agreed with the use of both measures. However the survey also asked whether the existing 'crime to conviction ratio' should continue until the new data is ready, 91 per cent of respondents agree the series should continue for the time being.

However the MoJ response notes: "Those who supported the continuation of ratios acknowledged the figures should be strongly caveated so users were aware of the limitations."

From the Summer of next year onward, the MoJ aims to use the new measures for conviction rates. In the mean time "clear guidance" will be published along side the conviction ratios.

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