The Forensic Science Service (FSS) Ltd. is only one of a number of commercial forensic suppliers involved in cannabis testing. By no means all cannabis seizures are forensically tested. The Home Office publishes annual figures for the volume of cannabis seizures in the annual National Statistics bulletin “Drug Seizures England and Wales”. The latest one covering 2006-07 was published on-line at:
www.homeoffice.gov.uk/rds/pdfs08/hosb1208.pdf
the 2007-08 edition will be published on 7 May. The Home Office does not collect figures on the percentage of seizures analysed by individual suppliers. However, as the FSS is the largest forensic supplier, it is likely that it tests around two thirds of the total seizures referred for forensic analysis.
Cannabis seizures made by law enforcement agencies are usually submitted to the Forensic Science Service (FSS) Ltd. to provide only a confirmed identification and weight. Only a small proportion of cannabis seizures are further examined to determine the tetrahydrocannabinol (THC) content, as a result of a customer request; customer requests for cannabidiol content are extremely unusual.
The table sets out the number of records and total weight of herbal cannabis and cannabis resin examined in the last 10 years by FSS.
Data derived from the Home Office Cannabis Potency Study 2008, show that when measured, the cannabidiol content of herbal cannabis has consistently been found to be less than 0.1 per cent. The cannabidiol content of cannabis resin varied between 0.1 to 7.3 per cent., with a mean content of 3.5 per cent. In today’s market, seizures of cannabis resin are comparatively rare compared to herbal cannabis.
Herbal Cannabis Cannabis Resin Plant1 1999 Number of records2 4,499 5,433 — Total weight submitted (kg) 1,525.8 6,732.5 — 2000 Number of records 5,904 6,572 — Total weight submitted (kg) 972.9 6,618.6 — 2001 Number of records 6,429 5,591 — Total weight submitted (kg) 1,414.1 3,296.5 — 2002 Number of records 11,687 9,346 357 Total weight submitted (kg) 2,278.4 5,126.5 — 2003 Number of records 11,139 7,100 1,410 Total weight submitted (kg) 3,261.3 6,954.3 — 2004 Number of records 9,306 5,202 1,365 Total weight submitted (kg) 1,267.2 3,638.2 — 2005 Number of records 9,899 4,463 2,927 Total weight submitted (kg) 4,118.3 4,281.8 — 2006 Number of records 9,309 3,285 3,858 Total weight submitted (kg) 1,568 3,576.6 — 2007 Number of records 10,250 2,459 5,466 Total weight submitted (kg) 2,989 1,075.9 — 2008 Number of records 11,916 3,238 6,235 Total weight submitted (kg) 2,659.8 11,615.9 — 1 Prior to quarter three 2003 cannabis plants were mainly recorded as herbal cannabis. 2 A record approximately equates to an individual item or exhibit. A seizure of cannabis or cannabis resin made by a law enforcement agency can consist of one item, a few items, several items or occasionally more.
The Forensic Science Service (FSS) Ltd has provided data in the following table. Only data from 2001 are readily available. The company reports that it is asked to test for tetrahydrocannabinol (THC) content only in a small proportion of the seizures referred to them for analysis.
Data on average THC levels of cannabis have previously been published in the Advisory Council on the Misuse of Drugs' Reviews of Cannabis up to the year 2007. Data for 2008 can be found in the Home Office Cannabis Potency Study 2008, published by the Home Office Scientific Development Branch, using test data prepared by the FSS. Another source of reference for 2005 is D. J. Potter, P. Clark and Marc B. Brown, Potency of D9- THC and other Cannabinoids in Cannabis in England in 2005: Implications for Psychoactivity and Pharmocology, J. Forensic Sci., 53(1), 90-94, 2008.
THC range1 Seizure year2 Data <=3 per cent. 4-6 per cent. 7-10 per cent. >10 per cent. Total per cent. 2001 Number of samples 2 11 13 19 45 2002 Number of samples 13 14 19 37 83 2003 Number of samples 22 21 33 88 164 2004 Number of samples 12 13 25 113 163 2005 Number of samples 10 8 33 178 229 2006 Number of samples 9 36 94 176 315 2007 Number of samples 21 71 120 137 349 2008 Number of samples 15 39 70 203 327 2009 Number of samples 1 3 11 34 49 1 THC = tetrahydrocannabinol 2 Data before 2001 are not readily available