A state of Injustice - - Dr Robert N Moles

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Chapter Two - Police and Forensic Science Procedures

Police duties include a wide range of activities such as education, crime prevention, directing traffic and managing their own resources. However, their principal duty is to investigate crime or possible crimes. In criminal investigations, the duty of the police (just like that of the prosecutors) is to serve the interests of justice and not just to obtain convictions.

In their investigation of crime it is necessary for the police to work with a wide range of technical and specialist people. Among the most important of those are the forensic scientists and pathologists. The word ‘forensic’ is derived from the Latin word forens, meaning a ‘tribunal’. It means ‘in connection with the courts’; it does not of itself mean ‘scientific’. Forensic scientists are those who use their science training for the investigation of crime; for example, biologists and chemists who examine blood, fluid or powder residues from a crime scene. Their expertise helps the police determine what might have happened and who may have been involved. The forensic pathologist is a medical doctor who has specialised in the study of pathology and works in the court environment. This often involves the examination of a dead person to collect appropriate samples or evidence. Forensic pathologists generally do not work with living victims such as those of sexual or other assaults, fires or road accidents. This is normally the province of a police medical officer.

The delivery of forensic science services varies between the states. In Adelaide, forensic scientists and pathologists are based at the Forensic Science Centre . Sometimes the Coroner’s office will be located with the forensic services (as it used to be in Adelaide) or near to it. The police forensic unit may also be nearby. In South Australia, if a person has died in circumstances where the cause of death is either unclear, or unlawful behaviour is suspected, the body is usually taken to the mortuary at the Forensic Science Centre. Under the instructions of the Coroner, a forensic pathologist will then examine the body (conduct an autopsy) and take samples for further examinaton. At the same time, police technical services officers will be working on the crime scene collecting other samples for examination by the scientists. The police forensic science section might also employ scientists to do some of this work. This chapter sets out the way in which the police are expected to approach the examination of a crime scene and the principles which they should have in mind when doing so.

Provision of Forensic Services

While forensic science centres may be organisationally independent of the police, the fact is that the bulk of their work comes from the police, who pay for the scientific services provided to them. This is important because the basic principles of science are neutrality and objectivity. In contrast, the basic principle of human and social organisation might be said to be ‘the one who pays the piper calls the tune’. A recurring concern within this area of work is whether the police are getting objective advice from the scientists – or advice that supports their need to secure convictions. A dilemma for defence lawyers is whether they can trust forensic scientists to provide them with objective and impartial advice when the scientists are so close to the police – or when they might be working with the police on the same prosecution case.

There is no particular reason why forensic science organisations have to be government departments or even substantially dependent on government funding. In some countries there has been a move away from such arrangements. In the United Kingdom and the United States, a number of commercially based and independent forensic science laboratories have been established, and it has been recommended that the government system in the United Kingdom be privatised. [1] When the police or defence lawyers in those countries have forensic work they are able to send it to any of the independent laboratories. Choice will be based on cost, turnaround time and quality of service. Such laboratories can provide services to anyone who requires them and for any reason. They might do testing for the prosecution, the defence, private individuals or commercial organisations. The people who require such facilities have a range to choose from – and the laboratories become accustomed to servicing a wide range of needs from a diverse group of clients.

Whatever the local laboratory arrangements, it is clear that the need is for good experts such as pathologists, biologists, physicists and chemists who can assist with the criminal investigation process.

Forensic Specialties

The police use many types of specialists and scientific disciplines to investigate cases. The most commonly used are the following:

Anatomy is helpful in understanding the cause of death or of injuries when dealing with skeletal remains; for example, to discover if the bones found in the back garden are human remains or a long dead pet. While not very accurate as yet, facial reconstructions from skulls are increasingly resorted to in investigations.

Botany and geology are used to determine where bodies, clothes or tools have been. Leaf, twig and soil samples left on clothes, tools or vehicles can be precise indicators of localities where events have occurred.

Chemistry is important for much of the standard work of the forensic scientist or pathologist. A detailed knowledge of chemistry is needed for the examination of powder residues from gunshot wounds, the aftermath of explosions and the identification of accelerants used to start fires in arson cases. Chemical tests help to identify materials and whether they are likely to have a common origin. Chemistry is also essential in the examination of documents and inks used in printing or writing. Histology, the procedure of preparing tissue samples for examination using the microscope (for example from an organ such as the heart or lung) relies on chemical staining processes to detect the features being analysed. Likewise, toxicology uses chemistry in the detection of drugs and poisons. Chemistry is also used to detect fingerprints, bloodstains, semen, urine and paint marks in almost every type of material and surface.

Entomology is useful where there has been insect infestation of a dead body – especially by blowflies – as this can help establish a time of death. This is particularly the case where death has occurred in the open and the body has not been found until after about 48 hours, when the other methods of timing death are less helpful.

Molecular biology helps identify semen, saliva and bodily fluid stains, significant in sexual assault cases, as well as blood, which is often fundamental in bodily harm and homicide cases. The detection, analysis and storing of fluid and tissue samples, and their use for DNA typing purposes, involves complex chemistry. DNA analysis has become very important to the investigation of crime and to the reconsideration of convictions.

Odontology is used for identification. Tooth enamel is the most resilient material in the body and the teeth may be the only way to identify remains that are skeletal, charred or decomposed. Bite marks can be very useful. On occasion, a thief has regretted leaving an apple core or half-eaten chocolate bar at the scene of a crime. Bite marks have also been used to identify assailants in cases of sexual assault and child abuse.

Physics provides an understanding of how things come into contact with each other. From ballistics to blood, from vehicles to knives, physics can help determine speeds and angles, which in turn may indicate the order in which things happened. This enables the police to check the stories and explanations that people have provided. Ballistics is the part of physics dealing with guns and ammunition. Fluid dynamics is the physical basis of bloodstain pattern analysis, which can reveal a good deal of information about the scene, including the way in which a weapon was used. Variable wavelength light sources are used to check for glass, fluid and powder residues, including traces of blood, semen, drugs and other materials. They are important in colour comparisons of  fibres, paint chips and inks. The physical matching of fingerprints, foot marks, tyre marks, tool marks, bullets and guns, all involve complex pattern-matching techniques – and an understanding of the physical dynamics that cause impressions in different materials and surfaces.

The Principle of Transference

Investigators gather physical evidence to establish if a crime has been committed, who may have been involved and how it may have been undertaken.

From his study of dusts in France in the early 1900s, Dr Edmond Locard developed what is now a fundamental tenet of forensic science – that when a person commits a crime they will leave at the scene something that was not there before, and carry away with them something that was not on them previously. This is now known as Locard’s principle of interchange (or transference) and is the basis of scientific crime detection (and the ‘clue’ in detective stories!). It is often summarised as ‘every contact leaves a trace’. [2] Thus, where a person has been murdered, the killer will leave vital clues at the scene of the crime – and also take away some material with them (on their shoes or clothing, for example) which will connect them with that scene. They may leave fingerprints, footprints, hairs or fibres, tool marks or car tyre marks at the scene. They may take with them mud, scratches, traces of blood or fibres from the victim, traces of broken glass or wood particles from a broken window.

Relevant evidence may be found on anyone knowingly or unknowingly associated with the incident. A fundamental operation, therefore, in any criminal investigation is to quarantine the scene immediately to avoid contamination and to preserve as much information as possible. The scene should be kept cordoned off until everything has been properly examined and recorded.

Contamination of crime scenes

Contamination means that the scene has been altered or interfered with after the criminal event, which makes reconstruction of the scene difficult. This may be accidental, as in the case of someone stumbling over the victim in the dark, or it may be intentional, as is the case with the criminal who wipes the fingerprints from the gun before placing it in the victim’s hand.

Contamination can also result from transference. The principle of transference applies as much to investigating officers as it does to criminals. It is the investigating officers who are the most likely people to accidentally transfer material into the scene and also between the scene and the suspect’s location. Officers who have attended at the crime scene should not be involved in interviewing suspects without taking considerable care to avoid transferring material to suspects and thus contaminating any evidence they collect from them.

Police Forensic Procedures

Any organisation has to have rules which identify the people who have the power to act for it. The police call their rules General Orders. Every police force will have rules relevant to the control and examination of crime scenes. In South Australia the police ‘Crime Scene and Forensic Procedures Manual’ is part of the ‘General Duties Manual’, which in turn is part of the General Orders.

A police forensic procedures manual contains the minimum operating standards crime scene examiners must follow when investigating physical evidence. Such a manual spells out the command and responsibilities issues such as who is in charge of each situation and who does what. It covers matters such as securing the scene, the role and responsibilities of the crime scene investigators, preparations and procedures for the examination of crime scenes and the preservation of evidence, communications (codes and procedures) and case management. It deals with practical topics such as photography, equipment and supplies required (such as adhesive tapes, fingerprint powders, plastic bags, gloves, overalls, cameras and film).

In this book we elaborate only on those aspects that are pertinent to the cases which we discuss.

The crime scene examiner

Crime scene examiners are usually part of the technical services branch of the police service. They are specially trained and are responsible for providing high quality physical evidence services to, or beyond, the standard specified in the guidelines. Where an examiner considers the task is beyond their knowledge or experience, they must seek assistance from a more experienced examiner or supervisor. Other police officers take statements and generally seek any relevant information to help determine what has happened.

Quarantine the scene

The police procedures state that for any unexplained death, the scene is to be cordoned off immediately. This means that crime scene tape is placed around the scene, leaving only one point of access. A guard is stationed at that point to control access and must have clear instructions about who is allowed in. A list is kept of all those entering and leaving the scene, including times of entry and exit, and such details as the protective clothing being worn. A crime scene examiner enters the scene via a route which permits access without disturbing any evidence.

Crime scene examiners must assume sufficient control of the scene to ensure that they can undertake their duties without interference. The police in charge of the investigation should be informed when the scene can be released to them and they can be shown through it.

The scene examiners wear gloves, overalls, shoe covers, face-masks and head coverings. This is to protect not only the scene from the examiners, but to protect the examiners from the scene. They do not know if anyone there has been suffering from an infectious disease, or whether there may be chemical agents or poisons present. Fluids at the scene might be bath water or bodily fluids. Everything is to be treated with the greatest suspicion.

It is important to think about what counts as the ‘scene’. Other locations and vehicles may also need to be secured. Where this is the case, a scene coordinator should be appointed to ensure that there is no cross-contamination. For example, a person attending at the scene should not be sent to interview suspects, or to attend at other locations.

Crime-scene examination

The procedures require the police to investigate the circumstances surrounding a sudden, violent, unnatural death, or other death, when it is not possible to obtain a death certificate from a medical practitioner. The investigation should provide accurate and detailed information on the manner and cause of death and the identity of the deceased. Deaths can be classified as natural (that is, died of natural causes such as a heart attack or old age) or unnatural. Unnatural deaths are further subdivided into accidental, suicidal or homicidal. The cause of death is usually provided by a pathologist.

An unexplained death is where a person is found dead but there are no immediate means of determining how death occurred. The next step is to decide if the death is suspicious or non-suspicious. The mere fact that a death is as yet unexplained does not mean that it is suspicious. However, police are trained to treat   every unexplained death as suspicious (a homicide) until an explanation is forthcoming which either confirms or removes the suspicion. Indeed, the South Australian Police Forensic Procedures Manual states specifically: ‘Initially (regardless of the probable category) crime scene investigators must treat every death as a homicide to ensure that no vital evidence is lost.’ [3] [Emphasis in original]

It is essential to treat a suspicious death more carefully than a non-suspicious one. Normally, the doubts cannot be resolved until the results of the autopsy are known.

In unexplained deaths, the deceased is the most important part of the scene and safeguards must be in place to ensure that no unauthorised access to the body is permitted.

The chain-of-evidence

In criminal investigations, all relevant evidence collected must be clearly linked to the source from which it arises. The explanation from a piece of evidence to its source must be complete and unbroken. This is called the chain-of-evidence and it is of critical importance if criminal charges are to be laid. All items should have an item number, description of item, location, time and date of collection, identity of person collecting (initialled), general location (room, address) and, if being handed the item by another, that person’s identity. Proper records should be kept of the transfer of all evidence each time it passes from one person or place to another as well as of all processing that is done to it. This is especially important in relation to body tissue samples taken at the autopsy since these are subjected to a number of processes as part of the examination procedures.

A complete and unbroken chain-of-evidence will eliminate any queries regarding potential contamination of the item. Details and batch numbers of any specific chemicals used could be important to any later verification of processes.

Temperatures

It is fundamental to record the body temperature at an unexplained death,. This is usually done by a pathologist. To estimate the time-of-death it is necessary to know also the ambient temperature, that is, the air temperature, both within any room where the deceased is found, and outside. Likewise, the temperature is needed of water in baths, pools, rivers or the sea in which a body is found.

Without disturbing the body unduly, detailed examination and recording of features is undertaken. After death, physical changes can occur quickly and the pathologist performing the autopsy later needs to be provided with detailed information on any markings, colouring, swelling or other features seen on the body when first found, as these could change before the autopsy begins.

Preservation of evidence

Physical evidence refers to anything which is of a physical nature that can be seen by the naked eye. It can include vehicles or buildings, fibres or obvious footprints and fingerprints.

Latent evidence is evidence that is invisible until it is enhanced in some way, such as fingerprints that cannot be seen until treated with powder or light. It may also refer to microscopic evidence such as traces of dust or fibres.

Destruction of evidence means that evidence has been lost, removed or transformed in some way so as to make it unavailable or unusable. Clearly the first priority of police arriving at a scene is to ensure that evidence does not get destroyed. Criminals may deliberately try to destroy the physical evidence or cause the evidence to be contaminated or misinterpreted; for example,  by wiping away fingerprints, or burning the car that was stolen or used in a robbery.

Evidence can be destroyed accidentally, particularly if there has been a lack of planning in the approach to the scene. For example, if a body is found in a car, it might be the most natural thing in the world to open the car door to check that the person is in fact dead or to identify the body. However, the existence of any flies within the car might help an examiner to determine how long it has been since the car door was last open. Merely opening the door might result in the loss of such valuable evidence.

Contamination of evidence, just as for contamination of crime scenes,  occurs where evidence has been exposed to contingencies that make its interpretation unreliable. If physical evidence is to be used to prove the presence of a person at a particular place, and that person has either visited or been brought to the scene, then the reliability of the evidence may be put in doubt. For example, if a police officer had been involved in a murder or robbery, but was later present at the premises as part of the investigating team, then any physical evidence linking that officer with the scene is contaminated by the later lawful presence at the scene. This is why any crime scene must be cordoned off until all of the physical evidence has been obtained.

From the start of any investigation the approach must be that everyone is a suspect. One cannot assume that any of the people who turn up to the crime scene are beyond suspicion. This applies as much to the investigating officers as it does to the family and friends of a deceased person.

Search strategies

It is important to think through possible search strategies from the outset. The principles of inclusivity and non-reversibility must be understood and remembered. Once information or material has been contaminated or destroyed it cannot be recovered. Therefore the initial information gathering should be as inclusive as possible. The basic rule is ‘never trust anything to memory’. Diligent observation and recording are mandatory. Crime scenes are often charged with emotion, but all involved must remain calm and in control at all times. The examiner in charge of the crime scene should not relinquish control  until confident that all relevant information has been retrieved and secured.

Photographs and video

Photographs are taken to record the scene and also for use later to help reconstruct the scene and the sequence of events. Police services provide for specialist photography and processing. Video recording of the scene should always be considered as it enables larger and more complex scenes to be understood in terms of scale and the relation of items to each other. Lateral thinking is important in determining what counts as the ‘scene’. It could, for example, include cars or people in the area. It is not unknown for perpetrators to remain in the vicinity of a crime to watch the product of their work unfold. Sound and movement can obviously be of value.  Also, video can also allow the officers outside the cordon to appreciate what has happened so that they can take appropriate action.

Where there is a suspicious death, the body is the most important component of the crime scene. Crime scene examiners should photograph the body at the scene and at the subsequent autopsy using colour film and electronic flash. Photographs should include general, mid-range and detailed photographs of the body, photographs of the body in the body bag, and any other photographs requested by the pathologist. ‘When it comes to crime-scene photos, more is always better, and great is always best.’ [4]

When objects or items are moved at the scene, it is important to retain precise details about where they were in relationship to other items. Photography, video or a grid reference might be appropriate depending on the circumstances. A photograph of an object in a cupboard might be relevant, but a photograph of a gun or knife on the ground outside or on a beach may not be sufficient to identify its precise location. A proper system of measurements should be devised, so that afterwards people will be able to reconstruct the relationships between items.

Before items are removed or examined, any possible trace evidence on the item itself or in its immediate vicinity must be preserved. This may involve fingerprints or dust on the item, or dust or dust-free areas revealed when the item is moved. This can indicate if the item has been recently used, removed or placed in that location.

In certain circumstances, it may not be possible to move evidence without damaging it. Footprints, tyre marks and tool marks in friable soil, or non-removable items or materials, will not be able to be moved. In this case, photographs and plaster or flexible casts can be used to retain the distinctive features of such evidence.

Case management

A log of events or running sheet must be established by the first officer arriving at the location. It should record the names, arrival and departure times of everyone entering and leaving the scene and any other relevant information. The police and Coroner’s office keep running sheets as a record of what is happening in relation to each of their cases. Each case will have a case number and once this is established, a continuous note is then kept in relation to the handling of the case. Each time a request for information is made it will be entered into the running sheet. When the matter has been attended to, that will also be entered into the sheet. It is then easy to identify at any stage which requests are still outstanding.

As soon as possible, it must be established who has been at the scene prior to the arrival of the police and whether they have moved or touched any items. This will indicate if any evidence has been lost or contaminated, or whether there is a chance that it may be misinterpreted.

Case management meetings are an important part of the organisation between the various people involved in the investigation. They should include the primary (operational) investigative team, crime scene examiners, technical services experts and forensic experts. The initial meeting should be held as soon as practicable and follow-up meetings held regularly afterwards. It is important to have a meeting of everyone involved before any arrest trial or other conclusion of the matter. It is important also to debrief and to assess performances at the end of the inquiry. Accurate notes of meetings should be made and kept in the case file.

Strategic thinking

Communication strategies should be properly stated. It might, for example, be improper for the scientific officers to be in direct communication with the investigative officers. It might be improper for them to attend at the scene, or at an interview with a suspect. There should be procedures for peer review of autopsy and laboratory observations. Control samples, which are samples that do not come from the scene but from a known and independent source, should be used to test and demonstrate the accuracy of the system.

The biggest cause of contamination, however, will be because investigators have arrived at an explanation of what happened too soon. Once one can explain what has happened, there is an inevitable tendency to see only what fits that story, and not to see other (inconsistent) elements.

An assumption is the death of a good investigation.

Endnotes

[1] The Times (London), 19 July 2003

[2] Kind S & Overman M, Science against crime, Aldus, London, 1972, p. 23.

[3] South Australian Police Crime Scene and Forensic Procedures Manual General Order 8278 (1996) 5. Death.

[4] Bass B & Jefferson J, Death’s Acre, Time Warner Books, 2003, p.185.

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