Hinckley prosecutor says attack was premeditated

US Attorney Roger Adelman, opening the case against alleged presidential assailant John W. Hinckley Jr., said Mr. Hinckley made a ''planned, premeditated'' handgun attack on President Reagan. Mr. Hinckley's lawyers are presenting an insanity defense, saying he tried to commit suicide by taking an overdose of drugs six months before he fired shots at the President in March, 1981. The court has ruled that the prosecution must bear the burden of proof in the case, and show that Mr. Hinckley was sane at the time.