An independent autopsy report of the 29-year-old Beijing resident Lei Yang who died in police custody last week is set to be released.

The preliminary examination has been completed and more work is still underway, said Zhang Huiqin, professor with People's Public Security University of China.

"I've done a lot of autopsies in my life and this is the most comprehensive one I've ever done. The family entrusted the work to me and the society believes in me. I can't let them down." Zhang said.

The preliminary examination, which lasted more than 13 hours, includes an autopsy and pathological examination on Lei's body.

"The autopsy report is yet to be released, so we have to keep waiting for the pathological results", Zhang said.

"Next step we will conduct examinations on various organs and detailed pathological examination and toxicological tests," she added, "We are not only responsible for Lei Yang as an individual, but also for the society and the law."

Lei, a graduate of Renmin University, was arrested by plain-clothes officers on Saturday last week in Beijing's suburban Changping district for allegedly soliciting a prostitute and was dead within hours of being detained.

The case stokes long-held public concern regarding excessive force by police in China.