China's Supreme People's Procuratorate (SPP) said on Sunday that it has dispatched personnel to Shandong to examine a high profile case now being appealed in which a man was given a life sentence for killing a debt collector who sexually assaulted his mother, which sparked huge controversy over claims of police negligence.

Over the weekend, Chinese media and online forums were filled with news about the case after reports that the defendant's lawyer plans to sue local police for their alleged "inaction" in handling the case.

Yu Huan, aged 23, from Guanxian county under the city of Liaocheng was sentenced to life in prison in February after he attacked four of his mother's creditors with knife, one of whom died later in hospital, after they exposed themselves to his mother while demanding she repay her debt on April 14, 2016, news portal thepaper.cn reported on Saturday.

The case has sparked controversy over whether Yu's sentence is justifiable due to the local police's alleged inaction after being called to the scene before the attack.

The SPP said it will review all evidence; hear reports from the provincial court; and examine whether Yu's action meets the definition of "justifiable defense," "excessive defense" or "intentional injury." It will also examine whether the local police were negligent.

The Higher People's Court of Shandong Province also said on its official Weibo account on Sunday that it accepted Yu's appeal on Friday and has set up a collegiate panel to review case files and will hear the appeal according to legal procedures.

Yu's attorney, Yin Liqing, filed the appeal on February 24 and will also sue the local police for failing to carry out their duties while they were at the scene, which Yin says led to the killing.

According to the verdict by the Liaocheng Intermediate People's Court, Yu's mother borrowed more than one million yuan ($145,340) from Zhao Rongrong in July 2014, verbally agreeing 10 percent monthly interest. In April last year, Zhao sent four of his henchmen to Yu's office to demand repayment, including the man who was killed, Du Zhihao.

The local police were called to Yu's office by his uncle at 10:13 pm, but after questioning the quarreling parties for a few minutes, they left without detaining anyone. The dispute then escalated, leading to Yu attacking the loan sharks.