THIRTY-THREE years ago, Ai Hongguang robbed four people and murdered three who shared hostel rooms with him in Shanghai and in Zhejiang and Jiangxi provinces.

During the early 1980s, there was no surveillance record and no nationwide criminal database. Ai electrocuted his victims and then vanished. The only clue to a possible suspect was a partial fingerprint found at the scene.

In 2012, Liu Zhixiong, a criminal science specialist at the Shanghai Public Security Bureau, came across a similar fingerprint when he was sorting the fingerprints data.

“I have seen these fingerprints thousands of times and the characteristics of the lines are all deeply imprinted in my mind,” Liu says.

Sure enough, the two fingerprints matched, Ai was caught and the serial killer was sentenced to death with reprieve last year.

Liu is among 167 specialists at the Criminal Science and Technology Research Management Center of Shanghai Pubic Security Bureau.

In the past five years, about 95 percent of all homicides in Shanghai were solved. Last year the number soared to 99 percent. The criminal science center is a key contributor to that astounding success rate.

It was all the way back in 1247, during the Southern Song Dynasty (1127-1279), that the first use of forensics in solving a crime was systematically recorded in China. Back then a handbook for coroners, “The Washings Away of Wrongs” by forensic medical expert Song Ci, was produced. The book shows cases that involve examining a victim’s body, analyzing motives, probing crime scenes — and even testing an assortment of blades on a cow carcass.

Today, these Chinese criminal science specialists carry on with advanced technology, complex experiments and a spirit to get at the truth and assure that justice is done.

“We never give up,” says Liu about catching Ai three decades after his crime spree.

The center has created specialized departments including toxicology, physiochemical, DNA testing, other forensic testing, crime scene investigation and more.

The specialists usually don’t wear uniforms or come face to face with criminal suspects. Some don’t even visit the crime scene very often, yet through a murder weapon or flecks of blood, they bear witness to the truth.

DNA experts

As the first city in China to establish a DNA database, Shanghai now has more than 1 million DNA records and is adding 100,000 more every year. By cross-comparing data, personal information can be located within minutes.

As DNA is often the crucial forensic evidence in crimes, the specialists have to do their job with meticulous care. “Every word I sign in the DNA report I guarantee with my life,” says Ping Yuan, deputy director of the DNA department.

To enter the well-sealed department, there are two automatic doors — one opens and shuts before the other can open. In the laboratory, the pressure is a bit higher than outside to make sure outside air won’t flow into the lab and possibly contaminate the vulnerable DNA evidence.

The test might involve a drop of blood taken from a brick or a bit of cotton. Sometimes, just getting a bare sample requires most of a day since it’s small and deeply entrenched with other material. Once extracted, the sample is submitted to another lab and put into a box measuring 10mm square, with 96 tiny holes evenly distributed in it. The box connects with a cone-shaped device for further analysis.

Sometimes the specialists have to run a test over and over again before getting a solid result, according to Ping. “Each case is an examination for us, the difference is that we will have no chance to retest. One fault can lead to a catastrophic result, so we have to approach the truth as close as we can,” he says.

From explosive material to a drop of glue, animal fur to vegetable fibers, specialists in the center’s physiochemical department spare no detail. Their job is to test anything that might pin a suspect to a victim.

“What we do here is putting the evidence to the best use while also classifying and collecting all the data for future reference,” Wang Changfu, a senior specialist, tells Shanghai Daily.

Entering one of the labs, all kinds of exhibits in plastic bags — leaves, toothpaste, knifes and other items — are neatly arranged on a white table. Around them are microscopes of varying size. Whether taking samples or cutting sections, this is where the first step of testing occurs.

“Here we ensure each item of evidence remains intact,” says Wang. Specialists must examine often tiny, obscure grains, hairs, fibers and other minuscule pieces of evidence.

“But there is no way that ‘virgin’ specialists can handle the meticulous task like this. When they hold the scalpel, their hands start to shake,” Wang says. “They need to be helped, guided and encouraged, like what we were given when we first came through.”

Around 5am on August 26, a woman’s corpse was found on Zhongshan Road S. Wang went to the scene as soon as he got the call.

All signs indicated that it was a bus accident that caused the death, according to the investigator’s brief. But confirming evidence was lacking.

Wang then slid under the bottom of the bus and at the middle of its base found a dent and hair. It turned out the victim had been drunk and was sitting by the roadside. She was drawn into the bottom when the bus passed by.

Wang says his checking the bottom of the bus was a matter of experience. Finding evidence hidden in such unusual places is what the specialists are trained for, and he knows that vehicle bases often hide evidence.

Wearing a pale blue shirt, this well-mannered Shanghainese has worked in the police center for more than 20 years. His colleagues nicknamed him “the king of paste” since he is familiar with all kinds of adhesives. Even without looking through the microscope, Wang can tell their characteristics and uses.

Like Wang, the eight others in the department have their specialties: investigating fire scenes, testing steel sealing of automobiles, fiber testing, soil testing and numerous others.

Their work is never really done. They often choose a material commonly found in crime scenes or used by criminals, then collect all the samples they can find in the market and carefully test them, assembling the data for more effective examination in the future.

“Fundamental knowledge of physics and chemistry is the base while there is no end for learning,” says Wang.

Spending more than 20 years doing physiochemical tests and studies, Wang has changed from a novice to a senior specialist. Along the way, he has gone from a slightly chubby, pale young policeman to a thin, dusky man with lines starting to etch on his face.

He jests: “Forced by the pressures and tenseness of this job, I look so much different from what I used to be like that people might not believe.”

“It’s not that you have no time for rest, but when you take a case, even if you are off duty, it haunts you all the time until you fight the case out,” he is quick to explain.

Polygraph test

In the physiochemical department, there is a special team of two people who are in charge of polygraph tests. They are one of the few groups in Shanghai that do lie detection, which can be used as an important reference.

“Whether or not the polygraph can be used in court depends on the judges,” says Shen Jing, one of the lie-detecting specialists. “But we will not run the test without the consent of the suspect.”

During the test, the suspect sits on the chair while his arms and fingers are connected to a computer with wires. The two specialists sit in front of several screens, one asking the questions and the other managing the program. The room is bright, with white walls and desks.

The test, much of which seems like ordinary chitchat, takes about an hour.

“In fact we spend huge amounts of time getting to know the background of the suspect and the whole case. Each question and the sequence in which it is asked is exquisitely planned,” says Shen.

Shen and his partner are both physiologists. Their tone, pitch, pace and tempo in asking the questions are tactical. The graph gives data including pulse, blood pressure, respiration and skin conductivity while the subject is asked and answers a series of questions. The specialists then need to analyze the physiological responses based on the complex curves to give the result.

Toxicology

“Using a polygraph is not just a way to point to suspects but more importantly a way to prove one’s innocence,” Shen says.

According to Shen, more than half of the subjects sitting for polygraph tests are exonerated. “Some suspects will ask for the test since the police can’t eliminate them from the inquiry, which has taken a great toll on their personal lives,” he says.

The first thing hitting your eyes when entering Liang Chen’s office is a flattened sofa bed. “Drug cases are on the increase,” says the department head, so the specialists in the department frequently work overtime. The bed is for everyone who needs a moment of rest.

“No matter what social media says and demonstrates how devastating drugs are, the number of drug addicts and drug crimes keep ascending,” Liang says.

“With new-type drugs coming up, it is hard to collect a full database,” says Zhang Runsheng, a top-grade scientist in the department, which has a huge collection of equipment that maps various characteristics of drugs into graphs.

In 2004, local police took severe measures against ketamine, a medicine used mainly used for starting and maintaining general anesthesia. Back then, at most some 70 urine samples would be sent to the lab every day, a number that has skyrocketed today.

Each sample takes three to four days to test. In the past year, the specialists have developed a specialized testing mold that screens for drugs quickly with more than 98 percent accuracy.