Contamination in the lab has been discussed multiple times before but remains a major issue in laboratories. The importance of evidence in any criminal case is evident and aids in telling a story of the events that happened at a crime scene. The reliability of DNA evidence to convict or clear an individual has become a major analytical tool in investigations and court presently. DNA analysis is a scientific method for human identification but if the integrity of the evidence comes into question then important information is lost. This information plays a major role in an inclusion or exclusion of an individual. Precautions must always be taken while handling evidence and each substance should be seen as hazardous while assuming a blood borne pathogen exists.1
Why Contamination Happens
Contamination in the laboratory and at the location of the scene occasionally occurs due to improper techniques and untrained individuals during the collection and analysis of evidence. A standard procedure for analyzing any evidence especially with biological samples includes the use of personal protective equipment (PPE).1
Personal protective equipment protects individuals from contaminating themselves with diseases present in evidentiary samples as well as protecting the evidence of contamination from the individual. The use of this equipment includes disposable jackets, gloves, goggles, foot covers, and face masks while forgetting any of these items will increase the risk of contamination. The validity of DNA found in a profile pertaining to the crime will be used to link the criminal to the event and must show to be statistically accurate to include or exclude an individual.
Since the investigation of a crime requires the collection of probative evidence by a forensic team, police or medical examiner, the use of statistical data will help demonstrate the importance of proper handling by accounting for error rates or relationship between samples. Some times the only type of evidence that is collected at a scene is biological involving DNA which increases its importance in the case. The article “The Effectiveness of protective clothing in the reduction of potential DNA contamination of the scene of crime” deals with personnel collecting or investigating a crime scene and the use of protective equipment.2
All human beings shed cells and leave behind DNA whether it be from sloughed skin to saliva from talking. The use of protective equipment however will reduce the amount of contamination (i.e. DNA) found at a scene or in the laboratory left behind during processing from investigators. Proper equipment to be worn while examining evidence may include gloves, face mask, body suit, visor and booties for shoes. Forgetting to use or periodically change any of this equipment will increase the risk of disturbing any available DNA left by a suspect. 2 By following procedures to protect a crime scene the evidence will maintain its original location and...