'Chinese Holmes' completes mission impossible

By the time the bodies of the two women were found, all traces of evidence that could lead to their killer had been cleared.

This was the scene police saw this summer in a village near Changchun, capital city of northeast China's Jilin Province. Without any footprints,fingerprints or even cigarette butts, breaking the case seemed like a mission impossible.

But Feng Zhen, a forensic doctor with the Changchun Police, simulated possible murder scenarios, extracted suspected skin residue from the chaotic scene using a technique he invented called ultramicro DNA extraction, and eventually found an unknown man's DNA after testing.

Ultramicro DNA extraction, according to Feng, is a method for extracting DNA from cast-off cells such as skin residue or flakes using a special kit when limited evidence is left at a crime scene. The kit was designed by Feng and a company in the city.

"The method makes our extraction procedure much simpler than traditional means, thus reducing the DNA's chance of being contaminated, which means we can get as pure DNA as possible, make multiple identical copies of the DNA sequence, and find the criminal," the 37-year-old "Chinese Holmes" said.

Feng examined the scene again and extracted more than 30 cast-off DNA samples. After careful comparison and analysis, he and his team confirmed that all the samples were from the same man.

Changchun police then collected over 4,000 blood samples from and around the village for a comparative analysis and targeted a suspect named Zhou Xicai.

"How could you find me out? I have already cleared all the evidence!" Zhou asked police while being arrested.

Zhou, a vegetable vendor, confessed that he killed the victims, a mother and daughter, two weeks after quarreling with the mother. He got rid of all evidence, including his clothes, before escaping by motorbike.

Although less thrilling than what people see in the movie theater, Feng and his team experience "Crime Scene Investigation" every day.

He dreamed of becoming a policeman when he was a boy, and became a forensic doctor after graduating from China Medical University in 2002. His career with the police rarely involves fierce gun battles or explosions, but patience and scrutiny.

An unsolved case in 2009 shocked Feng so much it made him addicted to DNA research.

An old couple was murdered in Dehui, a county-level city under Changchun. With the technology at the time, police could only take blood samples or cigarette butts to do a simple DNA investigation, but found nothing suspicious.

"If the case happened now, it could be solved by new technology. As years pass by, trace elements have been decomposing, but I still cannot forget the appearance of the dead," Feng said, sighing.

For him, being a forensic doctor is like being an auto mechanic: an experienced one can tell what the problem is after only hearing the sound of the engine. Based on his investigation experience in murder, rape, and robbery cases, he has continued to make breakthroughs in DNA inspection methods.

"There is only one truth. As police officers in technical investigation departments, we should make every effort to get evidence that is as solid as possible," Feng said.