Rules introduced this week will enable prosecutors to better supervise police decisions to accept cases and begin investigations, a step lawyers hope will curb rampant abuses. 'We see often that on one hand, there are cases concerning common citizens which police should investigate, but they don't; on the other hand, in cases where officials are concerned, police interfere and investigate, even when these cases are not criminal cases,' veteran rights lawyer Liu Xiaoyuan said. The Supreme People's Procuratorate and the Ministry of Public Security jointly issued a pilot guideline on Tuesday setting out procedures on how such supervision could be strengthened. The former already enjoys the legal right to supervise the latter, but in reality that right is rarely used. Under the new guideline an information-sharing system must be set up between prosecutors and police at the same administrative level, where the police must regularly report to the prosecutors about cases reported to them and cases they are handling. Prosecutors must also respond to complaints from citizens. The prosecutors can ask police to explain their decision to accept or decline a case, and can order the police to accept or decline a case if certain criteria are fulfilled. In particular, if prosecutors find proof that the police might have illegally interfered in civil and commercial disputes, or investigated as a way to seek revenge, frame or blackmail someone or seek other illegal benefits, or the police used criminal detention or other measures before formal arrests were approved, the prosecutors could seek a written explanation. If prosecutors conclude that the case is one that should be left out of the criminal realm, they could order police to withdraw from the case. 'This guideline is significant since given that a police decision to accept a case or not is not categorised as an administrative decision, there's no way an aggrieved citizen could sue the police if the police refuse to investigate,' Liu said. 'Now at least they can complain to the prosecutors. 'But of course, like all Chinese legal documents, we must wait and see if this would work in practice.' The pilot guideline will take effect on October 1. There have been many cases of police illegally rejecting or accepting cases in recent years. Most recently, on August 10, rights activist and artist Ai Weiwei once again had his investigation request rejected by a Chengdu police station regarding an assault last year, when policemen beat up Ai in a hotel room to prevent him from standing witness at the trial of another activist, Tan Zuoren . The charge of defamation is particularly vulnerable to abuse. Legally, police can only proactively investigate defamation cases if the defamation resulted in severe threats to national interests and social order. But police often interfere if the person defamed is an official or in power.