The bedroom, which is something like 10 x 11 feet, has a pool of blood in the small corner of the room near the wardrobe and I assume more blood under the duvet. Why does the retired guy think that because there is a pool of blood (approximately 2 x 2 square feet) in the corner of the room that it was necessary for the three people to walk in that blood during the murder?
Rudy clearly had blood on his shoes because his prints go directly from the blood out the front door. Raffaele had blood on his bare foot, and experts have identified his print on the bath mat. Amanda's seems to have had blood (or fruit juice with haematic substance) on her bare foot and her foot print was found in the hallway. It seems that Rudy stepped in the blood while wearing shoes, and the other two stepped in the blood while barefoot.
Hendry jumps to all sorts of conclusions about what Meredith was wearing, the time of the murder, who did what in the room, that everyone walked into the corner of the room to get blood on their shoes, that the room was not large enough for three people to commit murder, that blood spatter goes in some direction even though it appears to go in a different direction. He's a nut ... a retired guy with nothing to do so he pretends to be an expert in crime scene analysis and injects himself in a murder investigation in a foreign country. Because he says what the Knox family want him to say, they have decided that a retired accident reconstructionist is now a crime scene analyst.