Karl Gebhardt (http://en.wikipedia.org/wiki/Karl_Gebhardt) was an SS doctor in charge of a number of medical experiments on concentration camp prisoners. After the war he was tried and executed, and rightly so.

Two of his subordinates were also tried. One, Fritz Fischer (http://en.wikipedia.org/wiki/Fritz_Fischer_(medical_doctor)) Was sentenced to life and served 15 years.

The other was Herta Oberheuser (en.wikipedia.org/wiki/Herta_Oberheuser). Let's read up on her:

She worked there under the supervision of Dr. Karl Gebhardt, participating in gruesome medical experiments (sulfanilamide as well as bone, muscle, and nerve regeneration and bone transplantation) conducted on 86 women, 74 of whom were Polish political prisoners in the camp. Oberheuser killed healthy children with oil and evipan injections, then removed their limbs and vital organs. The time from the injection to death was between three and five minutes, with the person being fully conscious until the last moment. She performed some of the most gruesome and painful medical experiments, focusing on deliberately inflicting wounds on the subjects. In order to simulate the combat wounds of German soldiers fighting in the war, Oberheuser rubbed foreign objects, such as wood, rusty nails, slivers of glass, dirt, or sawdust into the cuts.

What did she get? 20 years. How many did she actually serve? 5.

Of the 13 doctors convicted in the doctors trial (http://en.wikipedia.org/wiki/Doctors%27_trial)

Only Helmut Poppendick (http://en.wikipedia.org/wiki/Helmut_Poppendick) served less time in prison. What was Poppendick convicted of:

At the American Military Tribunal No. I on August 20, 1947, he was acquitted from being criminally implicated in medical experiments, but was sentenced to 10 years imprisonment for membership in a criminal organization, the SS. He was released on January 31, 1951.

So he wasn't actually even convicted for the medical experiments. So, in fact, Herta served the least amount of time of any doctor convicted of an actual real crime at the Doctor's trial.