2.1 The General Register Office for Scotland (GROS) holds details of all deaths which are registered in Scotland. By convention, deaths are counted on the basis of the calendar year in which they are registered rather than the year of occurrence (as the latter might not be known). GROS closes its database for a calendar year around the end of the following June, so the statistics for 2007 are based upon the information which GROS had obtained by June 2008. GROS classifies the underlying cause of each death using International Classification of Diseases (ICD) codes, based on the information which is collected on the medical certificate of cause of death together with any additional information which is provided subsequently by (e.g.) certifying doctors, the Crown Office, pathologists or Procurators Fiscal.
2.2 Drug-related deaths are identified using details from the death registrations supplemented by information from a specially-designed questionnaire, which is completed by forensic pathologists. GROS requests this information for all deaths involving drugs or persons known, or suspected, to be drug-dependent. Additionally, GROS follows up all cases of deaths of people where the information on the death certificate is vague or suggests that there might be a background of drug abuse. A copy of the questionnaire used in 2007 is included as an Annex. This enhancement to the data collection system was described in a paper published by GROS in June 1995 (see the References). It should be noted that there is a possibility that more complete information has been reported in recent years. For example, technical advances may enable pathologists to detect small quantities of substances that could not have been found in the post-mortems that were performed several years ago.