Introduction

The DNA specimen plays a very important role in cases such as sexual assault, homicide, mass disaster, missing person identification, etc. Though, the achievement for a forensic laboratory examiner is depended on the condition of the evidence, if the DNA evidence is in a good condition then the maximum chances of a successful DNA profiling takes place. But if the collection and preservation of the evidence are not in an appropriate way then the DNA evidence might be able to give better results. All the biological evidence is at a risk of deterioration which results in microbial growth and this occurs due to environmental conditions. So, careful storage, collection, and preservation are important to obtain useful information for DNA analysis. A standard operating procedure is required for DNA collection and preservation in several types of the scene of crime and these procedures should be followed by medical doctors and investigation officers in the course of a criminal investigation. The DNA material is generally extracted from the biological samples. The biological samples from which DNA material is extracted and analyzed are such as blood and bloodstains, tissues and cells, hair with follicles, semen and seminal stains, bones and organs, saliva, etc. In case of bite marks the saliva is present on the person’s clothing or skin. Blood, saliva, hair, sweat, vaginal fluid, and semen can be found on the pillow, bed cover, blanket, etc. in rape cases. In the crime scene investigation, DNA evidence plays a very important role, it helps in connecting the victim and perpetrator with the crime scene and helps in legal proceedings. And it also helps in the reconstruction of the crime scene and supports the statement given by perpetrators or suspects, victims, and eyewitnesses. The collection of evidence should take place step by step by the field investigator at the scene of the crime (Lee & Pagliaro, 2013).

The priorities of an investigator are to discovering the evidence, recognizing the evidence, examining the evidence, collecting the evidence, recording the evidence, identifying the evidence, and packaging and storing of the evidence, present the evidence in the court of law. To avoid the contamination proper handling of the evidence should take place at the crime scene investigation. The main purpose of the DNA evidence is to provide useful information that helps in connecting the perpetrator or suspect and victim with the scene of crime. Every scene of crime is unique. There is a need for proper marking, sealing, and packaging of evidence at the time of collection of evidence. After that send the evidence to the forensic science laboratory. The work of a forensic scientist starts from the scene of crime with evidence recognition and recovery. Sometimes the evidence left by the suspect at the scene of crime. After the collection of the evidence, they have to be properly analyzed in the laboratories. DNA evidence also helps in revealing the information related to corpus delicti, modus operandi, connecting or linking the perpetrator with the victim and weapon, helps in disproving or supporting the testimony given by the witness, helps in a personal identification of the suspect, proving a lead in the investigation.