The overall crime-detection rate in the first half of this year fell to the lowest level in eight years, and police said this was due to a dip in crimes that usually had a high detection rate.
Announcement of the 40.6 per cent detection rate - down 1.6 per cent year on year and the lowest since 2003 - follows complaints from police unions about low morale and a heavy workload. However, the force said this was not a factor and a union said complaints had dropped off in recent months.
'The main reason for the drop in the detection rate is a decrease in cases with higher detection rates, including wounding, serious assault, indecent assault and serious drug cases,' crime and security director Stephen Lo Wai-chung, said.
A police spokeswoman said that there could be multiple reasons for the lower figure, including how co-operative residents were in reporting cases, and said it had nothing to do with detectives' manpower.
In the first half of this year police unions and frontline detectives said they could not cope with a growing caseload and the force introduced several measures in April, including more justification for overtime payments and accelerating the transfer of officers to the detective force.
Police Inspectors' Association chairman Benjamin Tsang Chiu-fo said the union had received no more complaints from detectives since the measures were enacted.
After the previous low of 39.2 per cent in 2003, the detection rate from 2004 to 2009 ranged between 43.6 per cent and 45.6 per cent.
The overall number of crime cases in the first half of this year was 37,433 - 0.8 per cent lower than last year. But the number of deception cases and the amount of drugs seized recorded a drastic increase.
Deception cases rose to 2,871, up 17.2 per cent, the highest in 10 years. This included 805 phone scams, up 26 per cent, and 391 internet commercial frauds, up 33.4 per cent.
Lo said 70 per cent of internet deception involved online auctions or shopping. The force cracked 228 auction cases and arrested 52 people in seven months. It worked with the Post Office and delivery companies to trace victims' property.
Police seized 83kg of heroin, up 112.8 per cent, 20kg of Ice and 157kg of ketamine, up 566.7 and 63.5 per cent respectively. The 8kg of cannabis seized was a rise of 166.7 per cent.
Lo said there was no information showing that drug cases had become more serious in Hong Kong.
'In the past 10 years, there have been rises and falls in the amount of drugs seized, including heroin, ketamine and cannabis,' he said. 'The numbers of seizures are related to many factors, like the amount produced, demand in different territories and the source of intelligence.'
Some 16,181 'quick cash' crime cases were recorded in the first half of the year, up 2.4 per cent. Of these, 1,197 involved stealing metal, including theft of door gates and drain covers, which were up 32 per cent. Some 695 cases involved snatching of cash left behind at ATM machines, which recorded a 13 per cent increase.
Meanwhile, director of operations Paul Hung Hak-wai said allegations by a Hong Kong newspaper that three off-duty officers were arrested with prostitutes during an anti-vice operation on the mainland two weeks ago were untrue. Mainland authorities confirmed no police officers had been arrested and investigations showed the officers referred to were in Hong Kong at the time.