Homicide in Scotland 2020-2021: statistics

Annex - Data Quality Statement

The statistics presented in this bulletin are based on a snapshot of Police Scotland’s live homicide database at an agreed date. Police Scotland maintain a continuously updated list of homicide cases that the Scottish Government uses to populate its own database of homicides in Scotland.

The data provided by Police Scotland go through a series of validation checks, whereby any queries raised through this quality assurance process are fed back to Police Scotland for consideration and discussion. It should be noted that homicides are very high profile crimes, and – in many instances – discussed openly in public. Both Scottish Government statisticians and homicide specialists within Police Scotland consider it unlikely that any major errors exist (as opposed to our practice outlined below for making revisions).

Since it is a ‘live’ system, amendments to Police Scotland’s database can arise after the data has been submitted to the Scottish Government (for example, a serious assault may be reclassified to a culpable homicide sometime after the crime was first recorded by the police).

To allow for these changes, we make retrospective revisions to earlier data for all years since the formation of Police Scotland (i.e. 2013-14 onwards). There were two such cases this time, one in 2018-19 and one in 2019-20 – as such the total number of homicide cases published in last year’s bulletin has been revised upwards from 62 to 63 for 2018-19 and from 64 to 65 for 2019-20. Earlier revisions are detailed in Homicide in Scotland, 2019-20.

As National Statistics, this information on homicide in Scotland is subject to continuous review by analysts to ensure it remains of high value for users. When producing the 2017-18 statistics, we identified that there is a tendency for the first publication of figures for a particular year to be revised upwards in subsequent bulletins - due to developments with specific cases. As outlined above, an example of this could be where a victim of serious assault dies of their injuries sometime after the incident, which could subsequently lead to the case being reclassified to a culpable homicide. Decisions at the prosecution stage can also have an impact, leading to some crimes being reclassified to homicides.

Given this, we made a small amendment to the data collection process for these statistics in 2017-18. As with earlier bulletins, we continue to present statistics based on a snapshot of Police Scotland’s live homicide database as at the end of the reporting year. However in addition to this, we now carry out a further check during the month before publication – whereby any crimes recorded during previous reporting years but not reclassified to a homicide until after the current reporting year, can now be included in the first publication of that year’s statistics – and not as a subsequent revision. There were no such cases in 2020-21.

This change further improves the quality of these statistics as it reduces the need for subsequent revisions to the data, though clearly they can still occur should crimes be reclassified to a homicide after the additional check has been carried out.

In addition to the above consideration of our revisions policy, we also previously discussed with Police Scotland the increase in homicide cases with a drug-related motive from 2016-17 onwards. Police Scotland advise that this may be due at least in part to an improvement in recording practice (i.e. better identification of where motives can include a drug-related element). Given this, users are advised to exercise some caution when comparing this variable with years prior to 2016-17.