The composition of Jeffrey MacDonald's pajama top is 65 percent polyester Dacron and 35 percent cotton. The yarns from the pajama top are a blend, while the sewing threads are composed of cotton. The color of the sewing threads is purple in most of the seams and blue-black in certain areas beneath the seam and in the piping on the sleeves. The sleeves of the pajama top are loose fitting and there are no buttons on the cuffs. The pajama top had been extensively laundered which weakened the sewing threads and removed a good portion of the dye from the threads.
In 1971, Paul Stombaugh studied the tears in the pajama top, and attempted to see if he could explain how the pajama top was torn. The pajama top was ripped down the left front seam, left shoulder, and left sleeve down to the cuff. Stombaugh concluded that someone grabbed the pajama top in the V-neck section and pulled down as Jeffrey MacDonald spun to his right. Jeffrey MacDonald has consistently claimed that the pajama top was pulled over his head by intruders and that it ended up around his wrists.
The tear down the left front seam and left sleeve of Jeffrey MacDonald's pajama top resulted in a proliferation of pajama threads and yarns in the master bedroom. The tear was over 72 inches in length which led Stombaugh to conclude that "when a garment is torn as the pajama top is torn, the bulk of the broken yarns and threads will become dislodged and fall off in the immediate area [where] the damage occurs." MacDonald insisted that the immediate area where the damage to the pajama top occurred was in the living room, but no threads or yarns from the pajama top were found in the living room.
Jeffrey MacDonald claims that he never got on the bed in the master bedroom nor did he get on the bed with either Kristen or Kimberley after he found them the morning of February 17, 1970. In addition, he states that he was not wearing his pajama top when he first discovered Kimberley and Kristen in their beds. CID investigators, however, found 28 pajama fibers on the master bed, 19 fibers on Kimberley's bed, and two fibers on Kristen's bed. A pajama fiber was also found near the headboard of the master bed where the word "PIG" was written in Colette's blood. Jeffrey MacDonald told CID investigators that he never approached the headboard nor did he even notice the word.
When medics lifted Colette's body off of the floor in the master bedroom, CID investigators William Ivory and Robert Shaw noticed a number of pajama fibers were located on the floor beneath Colette's body. Investigators eventually collected 24 pajama fibers in this area of the master bedroom floor. One of these fibers was located directly under Colette's head. Ivory noticed that this fiber was sticking up from a large pool of Colette's blood in pigtail fashion. CID investigators wondered how a proliferation of pajama fibers could end up underneath Colette's body when Jeffrey MacDonald insisted that he removed the pajama top from his hands and placed it across his wife's chest.