The investigation of a pedestrian’s death resulting from a hit and run accident is a crucial process involving several experts. Their objective is to uncover the truth using scientific evidence. Although not the primary cause, car accidents, particularly hit and run incidents, continue to occur distressingly often with tragic outcomes. This investigation focuses on an intentional hit and run case where the pedestrian suffered severe injuries from secondary impact before being struck by the driver.
Preserving a locus is of the utmost importance, so access is strictly limited to authorized individuals who need to examine the scene. Consequently, the initial police officer(s) at the locus assumes the responsibility of implementing procedures to preserve the scene [Saferstein, 2001]. These procedures entail closing roads, establishing boundaries, keeping scene logs, and occasionally documenting environmental factors, as evidence may be affected by weather changes.
Whenever possible, investigators gather information from witnesses, emergency personnel, and bystanders to obtain a description of what happened and gather any information about the individual or vehicle responsible. This information serves important purposes such as establishing the scene’s outer perimeter and determining the sequence of events.
Various other experts, such as the pathologist, the Prosecutor Fiscal, the photographer, the toxicologist, and the crime scene investigator, also work at the locus [Saferstein, 2001]. The crime scene investigator is the main person who determines who can enter a scene and sometimes establishes an entry and exit path during the examination of the scene. It is crucial for all experts to note and document all procedures and ensure that documentation is completed for future reference, which can be beneficial for the case.
The Prosecutor Fiscal is responsible for investigating and prosecuting a range of crimes, including sudden unexpected deaths and natural deaths like car accidents. Their primary objective is to establish whether a death is suspicious or natural. If there are any doubts, an extensive investigation takes place involving professionals such as pathologists, toxicologists, forensic scientists, and other experts with specific expertise.
The primary responsibilities of a forensic scientist involve examining physical evidence discovered on the victim at the crime scene and comparing it with evidence found on a suspect. Additionally, they provide expert testimony in court.
To identify potential evidence, an exhaustive search is carried out at the crime scene. This search entails analyzing tire marks, shattered glass, and paint smudges. Regarding vehicles, various layers of paint are applied including a primer, filler coat, and topcoat. If a vehicle makes contact with an object resulting in scratches, the car’s paint can be transferred onto that object.
By utilizing paint smears resulting from a car colliding or scraping against objects like lamp posts or barriers on the road, it is possible to determine specific characteristics of the vehicle involved in the accident. The chemical composition and color details of these paint traces can be used to identify the make and model of the vehicle through the international forensic automotive paint data query database (PDQ) [Royal Canadian Mounted Police (2005)]. After conducting an initial search and identifying physical evidence, photographs are taken of both the scene and all physical evidence.
Photographers employ a range of techniques for different environments, such as painting with flash and oblique flash techniques (Blizter 2002). Time exposure photography and painting with flash can enhance night scene examinations. Painting with flash proves particularly advantageous in dimly lit areas by supplementing additional lighting. Utilizing a flash unit enables long distance photographs to capture intricate details like vehicles, debris, and tire tracks that may go unnoticed in standard flash photography.
The composition of glass relies mainly on silicon dioxide (Si02), with variations depending on the type. When the deceased person crashed into the front window, the vehicle’s glass shattered and spread across the road. These fragments can also be found on the individual’s clothing, hair, and head injury. In future investigations, forensic specialists may compare these fragments to a known window sample in order to establish any possible connections [Curran et al. 2000]. Similarly, tire tracks can be examined in a similar way as shoeprints.
The forensic scientist examines tire marks, both latent and patent (2D) tire tracks, to gather information about the size of the tire. By consulting published references and electronic databases [Foster and Freeman (2005)], the scientist can then ascertain the make and model of the tire. Additionally, by comparing the dimensions of the tire with vehicle tracks, it becomes feasible to identify potential vehicles that may have employed these tires. If the vehicle is subsequently found, the tire marks can be used to establish a connection between the vehicle and the crime scene.
The Prosecutor Fiscal requests the forensic pathologist’s presence at the scene, as the death is considered suspicious. Later, in the mortuary, a two doctor autopsy is conducted due to the likelihood of criminal proceedings. The pathologists’ responsibility is to thoroughly establish the cause of death through internal and external examinations (post mortem), determine the circumstances surrounding the death, provide guidance on body recovery, preserve evidence on the body, and identify the deceased individual.
The pathologists will attempt to estimate the approximate time of death by measuring the body’s temperature via the rectal method or using a Henssge Nomogram. Several other factors can assist in determining the time of death. Rigor mortis, which is the stiffening of the body, begins to occur around 24 to 36 hours after death and typically disappears within 48 hours. Lividity, which is the pooling of blood due to gravity, becomes apparent approximately 1 to 2 hours after death and becomes fixed after 24 hours (Dr Rob Ainsworth, 18/01/11). Lividity can also indicate whether the body has been moved if it does not align accurately with how the body was found.
The post mortem is conducted by two pathologists. They initiate the examination by assessing external injuries, which can include recent or past injuries. In this particular case, there may be a significant number of injuries. The pathologists examine facial impact injuries that may have occurred when the deceased’s head collided with the front windshield. They also look for extensive scrape abrasions that can indicate the direction in which the body fell. Additionally, they search for drag marks on the body, which suggest that the driver ran over the deceased. The pathologists also take note of general characteristics such as height and weight, as well as any signs of illness or disease.
After the external examination, pathologists capture photographs as evidence and for future reference. The internal examination is then performed by one pathologist while the other observes and makes notes. Organs are individually extracted and examined, while samples are collected to determine the cause of death. In this specific instance, the pedestrian experienced a tertiary impact – being thrown into the air before landing head first on a car and subsequently on the ground.
The examination of the lungs is performed to determine if there was any asphyxia due to the fall, while the head injury is examined to identify any subdural or extramural haemorrhage that might have led to death. To evaluate the deceased’s condition before death, a toxicologist must conduct various tests on body samples. The responsibilities of the toxicologist involve analyzing these tests to establish whether toxins were used by the deceased, whether they engaged in long-term drug use, and if drug use had any relationship with the cause of death.
The pathologist obtains different samples for the toxicologist during the post mortem. These samples comprise femoral blood, urine, vitreous (found in the eye’s centre), bile, and cavity fluid (causes bloating after death). The analysed blood uncovers recent drug ingestion and substances present before death. Although urine may not always be accessible, it is more concentrated and can indicate prior drug use.
Hair analysis, similar to urine analysis, can be used as evidence of drug abuse. In this case, the pedestrian may undergo testing to determine if they were under the influence of drugs, prescribed medications, or alcohol; or if they were physically capable of taking care of themselves. It is possible that they have a medical condition that affects their understanding and actions. Once the autopsy and toxicology test are completed, the Prosecutor Fiscal will decide whether legal action should be taken. However, legal action can only proceed if the driver who caused the death is identified and captured.
After completing the post mortem examination, the Prosecutor Fiscal has the authority to release the deceased person’s body to their family, once they receive the death certificate. To investigate the death of a pedestrian in a hit and run incident, a team of specialists is needed, who work together to uncover the truth using scientific methods. As scientific advancements continue, the determination of causes of death can be done more efficiently and defendants can be accurately identified and brought to justice. The issue of car accidents is distressing, and with increased media coverage, it is hoped that more drivers will become aware of the dangers of reckless driving.
Referencing
Blizter HL and Jacobia J. (2002) Forensic digital imaging and photography. Academic Press, London, England. Curran JM, Hicks TN, and Buckleton JS. (2000) Forensic interpretation of glass evidence, CRC Press, Boca Raton, FL. Dr Rob Ainsworth, 18/01/11 – lecture notes Foster and Freeman (2005) TreadMate – A reference database of vehicle tyres and tyre tread patterns to assist the identification of vehicles from crime scene data, available at http://www.osterfreeman.co.uk, last access performed on November 22, 2005. Foster and Freeman (2005) SICAR 6—Tyre mark and shoe print evidence management system, available at http://www.fosterfreeman.co.uk, last access performed on November 22, 2005. Royal Canadian Mounted Police (2005) RCMP fact sheets: Pain data query (PDQ), http://www.rcmp.ca/factsheets/fact_pdq_e.htm, last access performed on November 22, 2005. Saferstein R. (2001) Criminalistics: An introduction to forensic science, T^ edition, Prentice Hall, Upper Saddle River, NJ.
