The International Olympic Committee has issued new rules for the London Games that start July 27 that would require checking testosterone levels in athletes whose eligibility as females is questioned.

Several elite female athletes have previously been accused of being males, including South African runner Caster Semenya (pictured), who was investigated and cleared after her 2009 world championship victory in the 800-meter event drew accusations from competitors.

The IOC says its intent is to identify athletes who would be ineligible “by reason of hormonal characteristics” — not to determine gender. But the policy has drawn criticism. Stanford University bioethicist Katrina Karkazis said the inclusion of a gynecologist and geneticist on the IOC examining panel contradicts this message. “It’s way more than a blood test or a series of blood tests. There will be genital exams, there will be genetic testing,” she said. Athletes will be disqualified to compete as females if they are found with testosterone levels typical of males, and if they possess cellular receptors that respond to the hormone’s effects.

“They chose something that really does discriminate between males and females,” said Dr. Joshua Safer, an endocrinologist at Boston Medical Center .