In his first day in court, a 39-year-old Chinese man admitted poisoning frozen "gyoza" dumplings that sickened 10 people in Japan 5½ years ago and triggered a scare over the safety of Chinese food products.
Lu Yueting, a former temporary employee at a food plant run by Tianyang Food in Shijiazhuang, Hebei province, where the dumplings were produced, also apologized to the victims at his first trial session Tuesday.
With Lu's guilty plea, the trial concluded after about three hours. There was no announcement of when the ruling will be handed down.
Lu was arrested in April 2010 and indicted that August. He is accused of injecting a toxic chemical into frozen dumplings using a syringe on three occasions in late 2007.
He was reportedly frustrated over his low wages and due to the fact that his wife, who was also working at the plant, did not receive a bonus payment when she took maternity leave.
Ten people in Japan fell ill between December 2007 and January 2008 after eating the tainted dumplings. Prior to Lu's arrest, relations between Tokyo and Beijing were strained as each side blamed the other.
The ruling on Lu, expected within several weeks, may have some impact on the relations of Asia's two biggest economies amid their current bitter territorial dispute.
According to Chinese criminal law, Lu could face capital punishment, a life sentence or 10 years or more in prison.
Normally, criminal trials in China are closed to foreign nationals, but the session Tuesday was open to a limited number of Japanese officials and reporters.
While a crowd of Japanese reporters assembled outside the district court in the morning under the watch of Chinese security officers, China's official Xinhua News Agency reported the start of the trial in an urgent dispatch.