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The chairman of the Constitutional Review and Law Reform Commission said defendants were using accusations of witchcraft as an excuse to kill people.
Police say at least 50 people were killed last year across the country.
In the latest suspected incident, a young woman accused of being a witch was burnt at the stake last week.
Correspondents say deaths and mysterious illnesses are sometimes blamed on evil curses and suspected sorcerers are often blamed and then killed.
Prosecuting those who kill these so-called magic makers within tight-knit communities is problematic, they add, and rural courts often acquit those who are made to stand trial.
"It's the easy way out for someone to kill somebody else, and use sorcery as an excuse," the head of the law reform commission, Joe Mek Teine, told the Australian Broadcasting Corporation.
"And you would find that the victim is totally innocent."
Mr Mek Teine told local media that the new legislation would force rural courts to charge those accused of sorcery-related killings with premeditated murder.
"It is a problem that has been existing in the country before the arrival of Western influence, and it's deeply rooted," he told the Post-Courier newspaper last week.
"The churches have done a lot to improve it but it's getting worse every time," he added.