The history of the Criminal Investigation Department's (CID) forensics division can be traced to the former Scene of Crime Unit, which started operations officially in 1977.
Back then, there were just 12 officers and no formal training.
"My only experience arose from my investigation work and on-the-job training," said security consultant Michael Won, 76. He set up the unit in 1975, drawing on his experience in presenting cases in court, where he learnt what evidence is needed and may be admitted.
"Our investigations were based on physical observations and (the) retrieving of objects, depending very little on technology," he said.
Before the unit was formed, officers with different specialisations had to be called in separately to document the scene, he added.
The quality of the evidence depended on "the enthusiasm of the investigation officer", he recalled.
Forensics officers have since gone on to play a crucial role in cases with mass casualties, such as the collapse of Hotel New World in 1986 and Nicoll Highway in 2004.
The forensics division now has about 100 officers.
In the past, officers had to plough through the archives manually to look for fingerprint matches, said Madam Lee Mei Fun, 54, who is the officer in charge of the fingerprint examination team.
Technology has since made a big difference, with an electronic fingerprint matching system in use now, she added.
Crime scene specialist Albert Pung, 63, said: "We started DNA analysis in 1991. (In the early days), if the blood stain was smaller than the size of a 20-cent coin, we didn't collect it as we probably couldn't get DNA from it."
He added: "Today, if I take a swab of your phone, I can get your DNA... science and technology has advanced so much."
Seow Bei Yi