The revisions to a key criminal law come after a wave of public complaints about the treatment of those detained by authorities.
The changes were welcomed with scholars saying they will offer better protection of suspects and reflect increasing awareness in China of the need for stronger detainee rights.
The formal introduction of the revised criminal procedure law to the National People’s Congress, which is in the middle of its 10-day annual session, ends six months of speculation and debate about whether the government would give police the legal authority to detain people for months at a time without telling their families.
Police have increasingly used the tactic over the past year to detain lawyers, democracy campaigners, and even internationally acclaimed artist Ai Weiwei.
The congress, which is controlled by the ruling Communist Party, is all but certain to approve the changes when the session ends on Wednesday.
There are two articles in the law that deal with notifying families, one in regular criminal cases and the other involving a type of detention known as residential surveillance.
In the case of residential surveillance, a type of house arrest that can happen in a fixed location that is chosen by police, a detainee’s family must be notified within 24 hours unless they can not be reached. Dissidents detained under this kind of residential surveillance are often put in suburban hotels or apartments, and many have reported being tortured by police.
“It’s not a picnic; it’s not fun,” said Joshua Rosenzweig, a human rights researcher based in Hong Kong. “It involves serious psychological and physical abuse. This is something that is facilitated by police having so much control.”
Mr Rosenzweig said abuses include being confined to bed for days at a time and holding fixed positions for hours, as well as constant police surveillance including when a detainee is using the toilet or in the shower.
In the case of regular criminal detention in jail or prison, families must also be notified – unless the cases involve the crimes of endangering national security or terrorism and authorities believe notifying the family would impede the investigation. Many dissidents are accused of threatening security, so the exception could still allow police to hold them secretly – but they would at least be in a formal detention facility, where abuses might be less likely to occur.
Chen Guangzhong, an 82-year-old professor at the Chinese University of Political Science and Law in Beijing who was critical of earlier drafts of the legislation, said the revised law marked a necessary curtailment of police powers.
“China is making further effort in improving human rights, democracy and the rule of law. In the past, judicial authorities had too much power,” he said.