A postgraduate medical student at Fudan University charged with killing his roommate by putting poison in their water dispenser, denied bearing a grudge against the victim and intentionally killing him when he stood trial on Wednesday.

Lin, 27, a winner of the national scholarship last year, put N-Nitrosodimethylamine, a toxic chemical that may cause liver failure, in the water dispenser of the room he shared with the victim, 28-year-old Huang Yang, on March 31. Huang died of liver and kidney failure on April 16.

Lin, a native of Shantou, Guangdong province, was arrested for allegedly intentional killing Huang on April 26.

During a seven-hour hearing at Shanghai No 2 Intermediate People's Court, Lin said the tragedy was an accident.

"Huang said on March 30 he intended to play a trick on some of our schoolmates as April Fool's Day was approaching," Lin said.

"I wanted to give him a hard time because of his arrogant statements, but didn't mean any real harm to him."

Huang and Lin, who were both enrolled in the Medical College of the university in September 2010, had shared a room since August 2011. Lin described their relationship as "not that close".

"He believed I didn't seek pleasure in life and I thought he was self-involved. But we'd never had direct conflicts and we chatted about our ambitions and exchanged personal views sometimes," he said.

According to evidence given by their friends that prosecutors presented at the court, Lin was infuriated by Huang when the latter several times talked about Lin's "cheap" living habits.

But Lin stated repeatedly that the crime was not planned and there was little rancor between them.

"Huang scored the highest in the preliminary exam for the doctoral study exam in March and Lin had an offer from the First Hospital affiliated to Sun Yat-sen University in Guangzhou. They both had brilliant prospects and it had nothing to do with jealousy," said Lin's attorney Zhou Bohong from Shanghai Jucheng Law Firm.

Lin told the court he obtained the toxic chemical from a lab at Shanghai Zhongshan Hospital where he had worked as an intern on March 31 and put it in the water dispenser.

The prosecution and defense expressed different opinions of Lin's knowledge of the toxicity the chemical.

Prosecutors said Lin confessed he had used the substance on rats in medical experiments and 10 out of the 70 rats, he believed, died of liver failure. He published his thesis in several academic publications with the toxicity of the substance clearly described.

However, Lin's attorney said there is no medical evidence to confirm the toxin is fatal.

"Nobody can say a person will die for sure or may face the possibility of death after ingesting the chemical," Zhou said.

The two sides also disputed whether Lin intended to kill Huang.

"Documents from the State Administration of Work Safety showed rats die when they are injected with 37 ml of the substance. The amount that Lin put in the water dispenser was around 50 ml according to a simulated experiment by police, and that was huge," prosecutors said.

Moreover, police found in the history of Lin's computer that he searched for the harm the chemical could cause on the evening he put the substance in the water, and some search results showed people died after ingesting 2 ml of the chemical, according to the prosecution.

"The chemical is a kind of yellow liquid with a pungent smell, so Lin believed Huang would be aware of the abnormal water and would drink no more than one mouthful," Zhou said.

Lin said he never thought Huang would die, even after he became ill.

"Most of the rats in my experiments survived and became lively again after 20 days as their livers healed by themselves. Although I knew Huang was transferred to an ICU ward on April 3, I always believed he was in the course of the disease and would recover after two weeks," he said.

In his final statement, Lin expressed his regret to the victim's family.

"My behavior caused Huang's death, which was a great blow to his family. I'm sorry for his parents and my parents who have devoted themselves to me for nearly 30 years. I accept any punishment from the court," he said.

The prosecution called for a severe penalty for Lin.

But Lin's attorney said Huang's death was not what Lin pursued so he should be charged with negligent homicide or indirect intentional homicide.

The court did not pronounce a verdict on Wednesday.

zhouwenting@chinadaily.com.cn