The city's top cop has admitted police investigators did not conduct a thorough enough search of Jakkrit Panichpatikum's car after the sportsman's murder.
Officers failed to find the former national sport shooter's mobile phone in their initial search of the car. A secondary sweep of the vehicle this week, however, uncovered the phone in a dashboard compartment.
City police chief Kamronwit Thoopkrachang said police were directly responsible for the oversight.
Jakkrit, 40, was shot dead by a motorcycle pillion rider on Oct 19 while he was driving his Porsche Boxster near Ramkhamhaeng Soi 166 in Min Buri district.
Police have already determined which roads the killer used to flee after the murder, according to a source in the investigation team.