Police have launched a formal criminal investigation into the case that Ji Zhongxing filed against security guards in Xintang village in Houjie township of Dongguan, in which he was allegedly beaten and maimed eight years ago.

Police confirmed that the investigation began in September. "But no details are available at the moment," police in Dongguan, Guangdong province, said on Tuesday.

Ji, 34, a farmer from Heze, Shandong province, was convicted of setting off an explosive at Beijing Capital International Airport in July. He was sentenced on Oct 15 to six years in prison by a Beijing court.

Ji and his attorney said that Ji set off the bomb because local officials in Dongguan had treated him unjustly after he was seriously beaten.

Liu Xiaoyuan, Ji's attorney, said police have set up a special task force to investigate Ji's case.

Liu also said Ji has decided to appeal the verdict to Beijing No 3 Intermediate People's Court.

"The punishment is too harsh," Liu told media after the verdict was handed down.

Punishment too harsh

Ji, who uses a wheelchair, was stopped by security staff while he was trying to distribute leaflets outside Gate B of the Terminal 3 arrivals hall on July 20. Ji then warned people nearby to get away before he set off the explosive, severely injuring himself and a police officer.

Ji has said he went to the airport to protest against an unresolved dispute related to an incident between him and two security guards in Dongguan in 2005. Ji alleges that the guards injured him so severely that he now has to use a wheelchair.

Liu said Ji will also file a lawsuit against the Guangdong Provincial Public Security Department and the Dongguan city government because the two agencies did not disclose information related to the investigation to him.

Ji's elder brother, Ji Zhongji, also said the verdict was unfair to his younger brother.

Ji Zhongxing was attacked and beaten by local security guards in Xintang at about 3 am on June 28, 2005, while he was carrying a passenger on his motorcycle.

Ji once said in his blog that his spine was seriously injured and that he has been paralyzed since. Ji's passenger, Gong Tao, also was injured in the attack, Ji said.

Lack of evidence

Ji sued the Dongguan government in January 2007, demanding compensation of 338,267 yuan ($55,500), but the court denied his request due to a lack of evidence.

Ji appealed to the Dongguan Intermediate People's Court in January 2008, but that court upheld the previous judgment.

In September 2009, Ji went to Beijing and petitioned the Commission of Politics and Law of the Communist Party of China Central Committee. The committee ordered Dongguan's police department to deal with the issue and, in March 2010, Houjie's public security bureau gave 100,000 yuan to Ji, according to a previous report from local media.

Yi Shenghua, a lawyer in Beijing, was quoted by Beijing News as saying that the result of the new Dongguan investigation will not affect Ji's sentence.

But as a "victim" of the Dongguan case, Ji's rights should be protected and respected, Yi said.