He said that his team and the laboratories they employed took special care to avoid contamination.
Researchers have found a reason for the puzzling survival of soft tissue and collagen in dinosaur bones - the bones are younger than anyone ever guessed.
Carbon-14 (C-14) dating of multiple samples of bone from 8 dinosaurs found in Texas, Alaska, Colorado, and Montana revealed that they are only 22,000 to 39,000 years old.
Members of the Paleochronology group presented their findings at the 2012 Western Pacific Geophysics Meeting in Singapore, August 13-17, a conference of the American Geophysical Union (AGU) and the Asia Oceania Geosciences Society (AOGS).
Since dinosaurs are thought to be over 65 million years old, the news is stunning - and more than some can tolerate.
Critics charged that the findings were mistaken or that what she called soft tissue was really biofilm produced by bacteria that had entered from outside the bone.
Schweitzer answered the challenge by testing with antibodies.
Her report in 2009 confirmed the presence of collagen and other proteins that bacteria do not make.
After the AOGS-AGU conference in Singapore, the abstract was removed from the conference website by two chairmen because they could not accept the findings.
Carbon-14 is considered to be a highly reliable dating technique.
It's accuracy has been verified by using C-14 to date artifacts whose age is known historically.
The fluctuation of the amount of C-14 in the atmosphere over time adds a small uncertainty, but contamination by "modern carbon" such as decayed organic matter from soils poses a greater possibility for error. Thomas Seiler, a physicist from Germany, gave the presentation in Singapore.