It was announced in Cape Town on Wednesday that State doctors who failed to treat Biko after he was tortured and beaten by security police will be examined by the Truth Commission.
Lang was quoted in a Port Elizabeth newspaper as saying nothing would be gained by calling him before the TRC.
"We have appeared before the Medical Council, there is nothing more to add," he said.
"There was nothing withheld at the time, it will be like trying to wring out a dry rag. If they say we should have acted differently, they must just look at my track record as district surgeon," he said.
"I now know with hindsight there are certain things I should not have done, but I genuinely believed what the police told me at the time. Only later did I discover what a bunch of liars they were. How many of us doctors could at the time have stood up and challenged the police?
"Only in the end did we realise there were things that did not tally. Never once did I ever refuse a patient the right to specialist treatment," Lang said.
The TRC is to hold a special hearing in June on the role of doctors and other health care professionals in perpetuating, colluding with and preventing human rights violations, commission member Wendy Orr said on Wednesday.
"One of the special submissions planned for the hearing is on the death of black consciousness leader Steve Biko," she said.
No one was prosecuted for Biko's death in 1977, but state doctor Lang was cautioned and reprimanded, and another state doctor Dr Benjamin Tucker dismissed from the profession in 1985 for faking reports on his health and failing to treat his injuries.