Scott Roeder, who has confessed to the fatal shooting of a Kansas abortion provider, is fighting prosecutors’ attempts to ban the so-called necessity defense at his trial. ... Roeders’ attorney filed a motion stating that Roeder should be allowed to argue that the killing was necessary to prevent Tiller from performing abortions.
The necessity defense is highly unlikely to succeed in Roeder’s case, according to two law professors .... “He may think this is his opportunity to explain why abortion is murder, but that’s not relevant,” said Michael Kaye, a professor of law at Washburn University School of Law in Topeka, Kansas. Also known as the “choice of evils” defense, the necessity defense is on the books in many jurisdictions and allows defendants to argue that they needed to take action to prevent greater harm. “Kansas has never to my knowledge recognized the necessity defense in its statutes, but sometimes defendants do raise it,” said Melanie Wilson, a law professor at the University of Kansas School of Law. In those cases, the court has declined to decide whether Kansas should recognize it, saying it’s a moot point because the defendant can’t meet the criteria for the defense. (Emphasis mine.)
For instance, the action that the defendant tried to prevent must be illegal — not simply perceived as immoral. If a woman has the right to an abortion under certain circumstances — and if the abortions that Tiller performed were lawful — then Roeder could not successfully argue that he was justified in killing Tiller to stop him from carrying out abortions.
Kansas courts have previously rejected necessity defenses.
--from the Southern Poverty Law Center