An Italian police official who conducted the original investigation defended her standards in court on Monday.
Patrizia Stefanoni took the stand as Knox's appeals trial resumed after the summer recess.
A verdict in the appeals trial is expected by the end of the month.
Knox has been behind bars since 2007. She and her co-defendant and one-time boyfriend, Raffaele Sollecito, were convicted of sexually assaulting and killing Meredith Kercher in the apartment that Knox and the 21-year-old Briton shared while studying in Perugia.
Knox was sentenced to 26 years in prison; Sollecito to 25. Both deny wrongdoing and have appealed the Dec. 29 verdict.
The Associated Press contributed to this report.