The victim, surnamed Lin, was a student at the former Nanjing Medical School. Her bludgeoned body was found in a sewer on March 24, 1992, but – possibly due to limited resources and technologies at the time – there was no clear lead on who the killer was.

Nanjing police had in 1992 offered a 10,000 yuan reward for leads – then worth US$1,818, or equivalent to five years’ salary for the average Chinese citizen – in a notice in the local Yangtze Evening News.

The notice also gave a sketch and description of the possible offender, described as a “male about 1.7 metres [5ft 7in] in height, about 25 years old, with a squarish face, big eyes, short hair, darker skin, scars or acne on his face, and a sturdy, muscular physique”.

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For years, the unsolved case haunted the police force. In a collection of police stories produced by the Nanjing Publishing House in 2012, former officer Ye Ning wrote that every year on March 24, Lin's parents visited the medical school’s campus in memory of their daughter.

One year, Ye saw Lin’s parents at the police bureau. “They left in calmness, although sadness and disappointment were written over their faces,” he wrote. “The couple held on to each other, and the umbrella could not shelter them from the rain.”

He was reminded that Lin and her parents still needed justice for her to rest in peace, he wrote.

Lin came from Wuxi, a city less than 200km southeast of Nanjing, one of her former classmates told Legal Daily. Another was quoted as recalling that they had reported to their teacher that Lin had not arrived for their class. The teacher found Lin’s umbrella in a faculty building, and then her body in a sewer.

The classmates said they had immediately informed Lin’s mother after learning that the killer may have been identified. “Lin’s father had died of lung cancer, her younger brother works in Shenzhen and her mother lives by herself in Wuxi,” one of the classmates was quoted as saying.

Ma is now 54 years old and had been running a dog trade business, according to a man quoted by Modern Express who said he had met Ma a few times in the early 2000s.

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The breakthrough in the case raised hopes among the Chinese public that another decades-old Nanjing murder, a notorious dismemberment case, could be solved.

In January 1996, body parts of a student were found boiled, shredded and wrapped in different bags all over the city, nine days after she went missing.

The victim, Diao Aiqing, was a first-year student at Nanjing University. Local police conducted large-scale searches around the city but never found the killer. The case has given rise to urban myths and been analysed in novels and posts on social media.

“I wonder when the Nanjing University case will be cracked, I hope it will be soon,” one person said on Weibo after the news about the Lin case.

The killer, 54-year-old Gao Chengyong, had created panic during the killing spree. Said to have targeted young women who lived alone, Gao was caught in 2016 after a tip-off and was executed in January.