Imagine you are a surgeon, and you have three patients - one of which needs a kidney transplant, one a liver transplant and one a heart transplant. The patients are honest, law-abiding citizens of society. Then a man, with all his organs perfectly healthy, walks in and collapses on the floor - he is a dishonest criminal who has killed three people and would have killed the next person he sees. Assuming nobody knew, you would kill the man and use his organs to save the three patients, amirite?

No because there are still other honest, law-abiding citizens who have been on waiting lists for a long time for transplants. You shouldn't put the others first just because. Not to mention that they would have to run multiple tests on the body of the guy and patients, have surgical teams help both remove the organs from the guy and put them into the other patients, then dispose of the organ-less body. There is no feasible way you wouldn't get found out which would then make you lose your job, medical license, probably your home, vehicle, and credibility. Also, there would be no way to prove that he would have killed the next person he saw.

That would make you just as bad as the criminal. People who need organ donations are put on a wait list, they don't need you to kill someone for them.

Nice thought, but like AndyBlacksmith said, you can't just yank out some organs and sew them up into someone else...it's a delicate process and the organs have to be matches for the people getting them.

me scared

Hippocratic oath

Everyone else pretty much covered the "it's unjust to kill someone even if they're a criminal part" but I'd like to add: being a surgeon doesn't mean you instantly know a person's past or their medical history. You would not know he were a criminal unless perhaps he was all over the news for his actions. Killing three people doesn't always make the news. Also, If the guy comes in an collapses on the floor, for one, you don't know he's healthy but him collapsing on the floor doesn't exactly make it look like he is. So even if you had permission to do such a thing, it would be stupid not to do proper tests on him to determine his health before you go shoving his organs into other people.

Overcoming the major medical flaws with this, and assuming you somehow knew for a fact that the man could donate all his organs and they'd be compatible with those of the patients, AND that you knew this about the criminal's mental state (specifically the fact that he's still dangerous), you would still have to add in one factor:
The man's organs cannot be donated, for whatever reason, to people earlier on the waiting list who have less time.

If that were the case, I agree, but i cannot, because i would then use the man's organs to do the aforementioned

Why not just use the organs out of that other poster's backpack? Apparently they carry them around...