Forensic Science Crime Scene Investigation
What is the role of a Forensic Scientist in a crime scene investigation?
Forensic scientist's primary role in a crime scene investigation is to collect, analyze and interpret physical evidence. They apply scientific methods and principles to assist in solving criminal cases. Their work often entails detailed examination of objects and substances found at crime scenes, such as DNA, hair, blood, fingerprints, and drug residues. They further provide detailed reports or testify their findings in court cases.
What types of physical evidence can a forensic scientist collect during a crime scene investigation?
A forensic scientist can collect several types of physical evidence. Common forms are body fluids (like blood and saliva), hairs, fibers from clothing or carpets, fingerprints, footmarks, tire imprints, bullet casings or weapons, glass fragments, and even digital data from computers or cell phones.
What is the importance of the chain of custody in Forensic Science?
Chain of custody is crucial in forensic science as it ensures the integrity of the evidence. It is the chronological documentation and physical evidence tracking method that records the seizure, custody, control, transfer, analysis, and disposition of the evidence. Mishandling or breaking the chain of custody can lead to contamination of evidence, and can even result in the evidence being ruled inadmissible in court.
What steps are taken to ensure the chain of custody is maintained?
Maintaining the chain of custody involves documenting every single person who handled the evidence, the date/time it was handled, and the purpose of handling it. The evidence is also properly stored and sealed with an evidence tape that will show if it's tampered.
What is DNA profiling and how is it used in Forensic Science?
DNA profiling, also known as genetic fingerprinting, is a forensic technique used to identify individuals based on their DNA characteristics. It is frequently used in crime-scene investigations, paternity testing, and identifying remains of a deceased individual. Each person's DNA is unique (with the exception of identical twins), making it a powerful tool for linking a suspect to a crime scene or ruling them out.
How accurate is DNA profiling in identifying criminals?
DNA profiling is extremely accurate when done properly. The chance of two unrelated individuals having the same DNA profile can be as low as one in several billion.
What are the primary types of fingerprints that forensic scientists look for at a crime scene?
The primary types of fingerprints forensic scientists look for are latent, patent, and plastic fingerprints. Latent fingerprints are not visible to the naked eye and require special techniques to visualize. Patent fingerprints are visible and are left by substances that stick to the fingers such as ink or blood. Plastic fingerprints are impressions left in soft materials, such as clay or wax.
How are latent fingerprints revealed at the crime scene?
There are various methods to reveal latent fingerprints, and the method chosen depends on the type of surface involved. One common technique is dusting the surface with fingerprint powder and then lifting the print using a tape. Other techniques involve the use of chemicals or alternate light sources such as UV light.
What is ballistics in Forensic Science, and how is it helpful in investigations?
Ballistics is the field of Forensic Science that deals with the motion, behavior, and effects of bullets, including the examination of firearms and ammunition. It helps in connecting projectiles and casings found at a crime scene to a specific firearm, potentially linking it to a suspect. This field also covers gunshot residue analysis which can indicate if a suspect discharged a firearm.
Can ballistics confirm if a specific gun fired a particular bullet?
Yes, it often can. When a gun is fired, unique marks are left on the bullet and cartridge case. Forensic ballistics experts can compare these marks with the ones on a suspected firearm under a comparison microscope. If the marks match, it can be concluded that the bullet was fired from the suspected gun.
How do forensic scientists use toxicology reports in crime scene investigation?
Toxicology reports are used to detect and identify drugs, alcohol, poison, or other chemical substances in a person's body. In crime scene investigation, forensic scientists use these reports to determine cause and manner of death, investigate drug-facilitated crimes, or if the person was under the influence of any substance at the time of the incident.
How are the samples for toxicology reports collected?
Toxicology samples are often obtained during an autopsy. Common types of samples include blood, urine, vitreous humor (fluid from the eyes), and tissues from various organs.
What is the role of Computer Forensics in crime scene investigation?
Computer Forensics, also known as Digital Forensics, focuses on recovering, analyzing, and preserving data found in computers and digital storage media to be used as evidence in investigations. This could include emails, browsing history, files, social media activities, or other digital fingerprints that can help build a case.
How is data preserved in computer forensics to ensure its admissibility in court?
Data preservation in computer forensics often involves creating digital copies or "images" of the storage media. This allows investigators to analyze the data without altering the original evidence, ensuring its integrity and admissibility in court.
What is forensic entomology and in what scenarios is it used?
Forensic entomology is the study of insects in criminal investigations, often to estimate the time of death. This is based on the lifecycle and development rate of insects that feed on decomposing remains. In addition, insects can also provide clues about whether the body was moved after death or if drugs were present in the body.
How does the lifecycle of insects help to estimate the time of death?
Certain insects are attracted to decomposing remains in a predictable sequence. The type of insects present, their stage of life (like eggs, larvae, or adult), combined with environmental factors like temperature, can be used to estimate the time since death or when decomposition began.
What is forensic anthropology and how is it applied in crime scene investigations?
Forensic anthropology is a special sub-discipline of physical anthropology that involves the analysis of human skeletal remains in a legal context. In crime scene investigations, forensic anthropologists may be called upon to determine the age, sex, ancestry, stature, and unique features of a decedent from the skeleton, to help identify unknown remains and determine cause or circumstances of death.
How can forensic anthropologists determine the cause of death?
By examining the skeletal remains, forensic anthropologists can often determine the cause of death. For instance, trauma to the skeleton like fractures or sharp force trauma, signs of chronic diseases or malnutrition can give vital information about the possible cause of death.
How is blood spatter analysis used in crime investigations?
Blood spatter analysis involves studying the size, shape, distribution, and location of blood stains at a crime scene to recreate the events of a violent crime. It can help establish the sequence of events, the direction of blood, the type of weapon used, and approximately from where and how the blood was projected.
Does the angle of impact influence the shape of the blood spatter?
Yes, it does. A blood droplet that impacts a surface perpendicularly (90 degrees) will be round, while blood that impacts at an angle will create an elongated bloodstain. By measuring the length and width of these stains, investigators can estimate the angle of impact.