Brian Monk, 35, a mechanical engineer, who is divorced from Katrina's mother Valerie Gaughan, 37, said: 'It must have been someone she knew. She was not naive and would not go off with someone.'
Katrina's body was found on Friday dumped in an alley in Enfield, north London about 50 yards from her home. The 12-year-old had been asphyxiated and a plastic supermarket bag taped over her head. She was last seen alive leaving a No 121 bus in Enfield on Thursday. Detectives do not know why she departed from her routine of walking straight home.
Mr Monk spoke as police examined 250 tons of domestic rubbish in an attempt to find clothes Katrina was wearing. Officers at an incinerator in Edmonton, north London, searched for the black bomber jacket, green school blazer, black shoes and fluorescent pink bag that were missing when her body was found. Refuse was collected from the area the same day.