Her killer did a bad job. It was amateur work: There were bloody fingerprints and footprints all over the apartment, and the killer even defecated in the toilet and forgot to flush. But that wasn't the worst of it. Whoever murdered Meredith Kercher didn't know how to use a knife.
The first two wounds weren't deep enough to do fatal damage, the knife catching on bone. On the third try, the killer found a soft spot in the left side of her throat and plunged the blade full to its hilt. The attacker then pulled the weapon from left to right several times in a sawing motion, then up and back, leaving a gash more than three inches long and three inches deep. It was clear, from the purposeful savagery of this final blow, that the intent was to kill. But since the blade missed the carotid artery, Kercher's agony lasted as long as 10 minutes. An experienced killer would have known better.