Introduction

Current methods used by forensic DNA laboratories are sensitive and capable of amplifying and detecting low quantities of DNA. With the ability to detect minute quantities of DNA, comes an increased chance of detecting contaminant DNA in both samples and controls. Contamination can happen during any step of the process and can result from a variety of substances, including plant material, bacteria, and human genomic DNA. There are occasions when the source of contamination cannot be determined and/or the incidences are sporadic in nature.

It is not always possible to prevent contamination; however, laboratories should ensure that procedures are in place to:

• Minimize the risk of contamination
• Detect contamination
• Document and implement corrective measures for incidents of contamination

This module focuses on extraneous human genomic DNA deposited after the crime event (during the collection and/or analysis process).

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