Blight of cannabis revealed by hunt for killers

Det Supt Karnail Dulku oversaw the investigation which spread as far afield as rural southern China as well as towns and cities across the UK to track down those responsible for the brutal murder of Chen Cai Guan.

The inquiry was one of the most complex cases ever undertaken by North Yorkshire Police, with many friends and associates of the victim unwilling to co-operate, fearing they too could become victims of an international drugs cartel

Officers delved into the murky criminal underworld of Chinese triads to provide one of the clearest insights yet into the intricate operations of cannabis production.

It revealed a complex web of financial deals with money-laundering operations is often behind the cannabis production, which in turn is linked to other major crime including human trafficking and prostitution.

Drugs cartels spanning the globe are becoming increasingly involved in the production of super-strength skunk cannabis, often opting to set up large-scale growing operations in isolated parts of the country to avoid detection.

The drug is on average 15 times the strength of normal cannabis and sells for up to four times as much, at more than 130 an ounce.

In North Yorkshire alone, police have carried out raids on more than 100 locations linked to skunk cannabis production in the space of only 12 months.

Det Supt Dulku said: "These people are interested in making money, as simple as that. They will get involved in any criminal activity if they can see that it will be profitable – and these crimes can prove to be extremely lucrative.

"There are different layers of people involved, making it all the more difficult to trace the main individuals behind the operations."

Mr Chen's body was discovered in March last year in a canal at Burn, near Selby. The murder investigation which was launched eventually led back to a major cannabis farm discovered a month before, 22 miles away on an industrial estate in Elvington.

Leeds Crown Court heard Mr Chen was murdered after falling out with co-workers at the cannabis farm believed to be attempting a double-deal with a rival criminal gang by selling on about six kilogrammes of skunk cannabis valued at between 15,000 and 20,000.

Det Supt Dulku said: "From the outset, this investigation proved challenging and complex. However, we were confident that we would solve the murder of the then unknown Oriental man whose life had been ended so brutally."

A 53-strong team of officers, who were aided by 19 police staff, was drafted into inquiry and detectives travelled to rural southern China, Mr Chen's home territory, as well as Beijing in a bid to collect vital evidence.

Colleagues also visited towns and cities across the UK including Doncaster, Sheffield and Manchester as well as London, Birmingham, Bristol and Aberdeen.

Officials from the Borders Agency, the Serious Organised Crime Agency and the Ministry of Public Security of the People's Republic of China were involved, and detectives were drafted in from South and West Yorkshire, the Metropolitan Police, Avon and Somerset and West Midlands.

Det Supt Dulku said: "Regardless of Chen Cia Guan's involvement in illegal activity, we were determined to find those responsible for his death and seek justice. In addition we wanted to prevent an escalation of this type of criminal vendetta homicide which, if left unchallenged, may have spread into our communities."

The convictions sent a clear message to organised crime groups seeking to operate in North Yorkshire, he added: "No one is untouchable and we will continue the fight against serious and organised crime and the negative effect it has on our communities."

Figures released by the Association of Chief Police Officers in August revealed more than 6,800 cannabis farms and factories were detected in the UK in 2009-10. More than 1.3 million plants with an estimated value of 150m were recovered.

Investigation on a grand scale

n A library of 3,881 exhibits was amassed.

n Officers took 3,135 statements and reports.

n More than 50,000 telephone numbers were processed

n A total of 53 police officers and 19 police staff worked on the investigation

n The services of 20 interpreters were used.

n Further arrests were made in addition to those for murder. Offences ranged from the production of cannabis, money laundering, fraud, theft and immigration offences.