On October 24, 1996, at 1607 central daylight time, a Cessna A185E airplane, N185XX, was substantially damaged during a forced landing near Giddings, Texas. The airplane was registered to and operated by a private owner under Tittle 14 CFR Part 91. The private pilot/owner of the airplane and one of his passenger sustained minor injuries, while a pilot rated passenger was seriously injured. Instrument meteorological conditions prevailed for the personal flight for which an instrument flight rules flight plan was filed. The flight originated from the Houston Southwest Airport, at approximately 1510, with the Robert Mueller Municipal Airport in Austin, Texas, as its intended destination. While in VMC cruise flight at 8,000 feet MSL, the pilot reported to ATC that the engine oil pressure was dropping and subsequently reported an overheating engine. The pilot requested vectors to the nearest airport. ATC controllers provided vectors and airport information for the Giddings-Lee County Airport; however, radio and radar contact was lost during the airplane's descend when 10 miles east of Giddings. Law enforcement personnel reported that the aircraft touched down on a westerly heading in an open field approximately 5 miles east of the airport, coming to rest approximately 1,500 feet from the initial point of ground impact. Examination of the wreckage by the FAA inspector confirmed that the right main gear collapsed and the right wing and fuselage sustained structural damage. The inspector added that the "underside of the fuselage was found heavily coated with fresh engine oil." In a telephone interview conducted by the investigator-in-charge, the pilot stated that the engine oil was changed by maintenance personnel at his hangar on the previous day. This was the first flight after completion of maintenance. The pilot added that an engine run up was not performed upon completion of the maintenance due to inclement weather on the day of the oil change. The pilot added that during the preflight inspection of the airplane, he did not find any evidence of an oil leak, either on the engine or the hangar floor. The engine was examined under the supervision to the FAA inspector. Examination of the engine revealed that an "O" ring seal (Part number CI48100-8) installed on the oil filter top, was pinched during installation thus allowing the engine oil to leak during operation to the engine. According to the engine records, on December 5, 1995, the engine was modified by the installation of an "Ultimate Engine Oil Filter" (Part number SA8922SW21) manufactured by Capehart Industries Inc., of Mena, Arkansas, under an FAA Supplemental Type Certificate dated July 21, 1994. The pilot purchased the airplane in April 1995.