Jim Kouri
Amanda Knox acquittal: Sloppy crime scene analysis created injustice
By Jim Kouri
October 4, 2011

The judges and jury have overturned American citizen Amanda Knox's conviction for murder of Meredith Kercher, in one of the most controversial international crime cases in the new millennium.

The 24-year old Knox appealed her December 2009 conviction regarding the death the 21-year old British student with whom she shared a cottage in Italy.

Originally convicted, Knox was sentenced to 26 years imprisonment in Italy. However, except for a defamation of character conviction for accusing a totally innocent man of killing Kercher, she is free.


When Amanda Knox became a free woman in Italy after more than two years of being the main character in one of the most analyzed crime stories in the new millennium, one factor involved in her acquittal: sloppy police work especially the crime scene investigation and analysis.

For example, the positive results of the preliminary blood examination at the crime scene did not take into account the frequent false-positives inherent with the use of luminol.

A wide range of domestic and industrial substances that might be mistaken for hemoglobin in the forensic luminol test for blood were examined. The substances studied were in the categories of vegetable or fruit pulps and juices; domestic and commercial oils; cleaning agents; an insecticide; and various glues, paints and varnishes. In a few cases the brightly emitting substance could be distinguished from blood by a small but detectable shift of the peak emission wavelength.

One of the first responsibilities at a crime scene is to prevent the destruction or contamination of evidence. Security measures must be initiated to prevent unauthorized persons from entering the crime scene or the immediate area. This includes members of the news media who may appear on the scene.

Detectives and officers must not touch, move or pick up objects or disturb in any manner articles, marks or impressions that may have been left by the criminal. Others must be prevented from altering or contaminating the area, as well.

Investigators should maintain this rigid security until all measurements have been made; the scene has been thoroughly searched for fingerprints, tool marks and the like; and all evidence has been collected.


Although various investigative guides can help a criminal investigator assess the value of evidence that may be found at a crime scene, the selection and collection of these items remains a question of individual judgement.

This personalized approach to the task of gathering evidence often leads to the common error of overlooking or disregarding the importance of the less obvious physical traces left by a criminal.

The investigator must develop a sensitivity to these things that may be out of place or do not appear to "belong" regardless of their size or appearance — mud on a rug, lipstick stains on a glass in a bachelor's apartment, a cigarette stub found in the ashtray of a known pipe or cigar smoker, cloth fiber hooked on a torn window screen, etc.

After the investigators have located an item considered pertinent to the case under investigation, it should not be disturbed until it is photographed, measurements are made, its position recorded on the crime scene sketch, its position recorded in the investigator's notebook, and, if the case warrants, until the item has been processed for latent fingerprints.

Crime scene protection is fundamental to a criminal investigation and must be initiated by the first officer to arrive on the scene. Not only will adequate security measures prevent the destruction of physical evidence, but the hazard of creating false investigative leads is also reduced.

© Jim Kouri


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Jim Kouri

Jim Kouri, CPP is currently fifth vice-president of the National Association of Chiefs of Police... (more)


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