[B][B]ANCHORAGE, June 21— [/B] In a Criminal Court matter of unusual significance in Alaska, Charles Meach 3d, charged with killing four teenagers in a park, entered a plea June 15 of ''not guilty because of mental disease or defect.'' [/B]
[B] Because of Mr. Meach, who used the same plea successfully in a 1973 murder trial, a new state law on insanity pleas was passed earlier this month, and the Alaskan way of dealing with the criminally insane has come under examination....