On December 6, 2003, about 1642 Pacific standard time, a Cessna 172S, N396TA, nosed over during a forced landing in a field about 4 miles south of Watsonville, California, after experiencing a total loss of engine power. The airplane was operated by the owner/pilot under the provisions of 14 CFR Part 91. The private pilot was not injured, and the airplane was substantially damaged. Visual meteorological conditions prevailed at the accident site, and an instrument flight plan had been filed. The personal flight originated at San Martin, California, at 1622, destined for Monterey, California. The pilot reported that he was en route to Monterey, at 2,400 feet mean sea level (msl). He was in instrument meteorological conditions when the air speed, rate of climb, and altimeter became erratic, and the electrical system went off-line for a second, followed by a rough running engine. The engine quit and failed to restart after three attempts. The pilot stated that icing was not an issue and "the temperature was 6" and he did turn on the pitot heat. He said he had 10 gallons of fuel in the right and left fuel tanks. Approach control vectored the pilot towards the nearest airport at Watsonville. The pilot said he entered visual conditions about 1,800 feet mean sea level, but was unable to reach Watsonville and landed in a soft muddy field and rolled inverted. The airplane remained inverted in the field for a period of time due to the muddy conditions that made recovery difficult. After recovery 4 gallons of fuel was recovered from the left fuel tank and about 1.75 in the right tank. Fuel was found in all components of the fuel system. The fuel selector was found in the "both" position. The emergency fuel cutoff was found in the off/closed position.