On February 5, 1995, approximately 1330 mountain standard time, N1403J, a Rockwell International 112B, was substantially damaged during a forced landing 35 miles northwest of Santa Fe, New Mexico. The private pilot received minor injuries and the passenger was not injured. Visual meteorological conditions prevailed. The following is based on the pilot/operator report and subsequent telephone interviews. The pilot departed Santa Fe, New Mexico, with full fuel tanks, and flew to Telluride, Colorado. He did not refuel while he was in Telluride. The airplane had been aloft for about one hour on the return trip to, and was about 35 miles northwest of, Santa Fe when a "serious vibration" developed that could be felt through the controls. All engine instruments were normal, but the pilot noticed a steady, gradual loss of airspeed and altitude. Despite the application of full power and alternate air induction heat, airspeed and altitude continued to decay. The pilot elected to make a wheels down forced landing on what appeared to be a suitable snow field. The airplane touched down in deep, soft snow and nosed over. The pilot said he had not flown in visible moisture during any portion of the flight, and the fuel selector was in the BOTH position at all times during both flights. The temperature and dew point at Santa Fe, 35 miles from the accident site, was 46 and 24 degrees, respectively. The engine was later disassembled and examined under the direction of a Federal Aviation Administration maintenance inspector. According to a report from Capital Aviation (see attachment), water was found in the fuel injection servo, induction galley and tubes, and cylinder intake ports. According to Capital's shop foreman, he found the induction air heat control in the OFF position. He manually moved the control several times and noted it appeared to operate correctly. The report further stated that "we suspect induction ice formed to such a degree, even with adding induction heat at notice of engine roughness, there was too much ice for the engine to overcome."