Use of forensic evidence in court

What Are The Problems Or Limitations Surrounding The Use Of Forensic Evidence In Court?


The origins of forensic science can be traced back to the 6th century with legal medicine being practised by the Chinese. Within the next ten centuries advances in both medical and scientific knowledge would contribute to a considerable increase in the use of medical evidence in courts. Other types of scientific evidence did not start to evolve until the 18th and 19th centuries, a period during which much of our modern-day knowledge on chemistry was just starting to be developed. Toxicology, the study of poisons, emerged as one of the new forensic disciplines, and was highlighted by the work of Orfila in 1840 with his investigation into the death of a Frenchman, Monsieur Lafarge. Following examination of the internal organs from the exhumed body, Orfila testified on the basis of chemical tests that these contained arsenic, which was not a contamination from his laboratory or the cemetery earth.

This evidence resulted subsequently in Madame Lafarge being charged with the murder of her husband, but more importantly raised the problem of contamination, a constant concern for any forensic scientist. During the latter part of the 19th century there was also considerable interest in trying to identify an individual. One approach, studied by Alphonse Bertillon, was to record and compare facial and limb measurements from individuals. This proved to be unsuccessful due to the difficulties in obtaining accurate measurements. However, this was the first recorded attempt in a criminal investigation to use a classification system based on scientific measurement. Interestingly and in accord with this principle, forensic scientists today use the results from a combination of analytical measurements to discriminate between groups or to compare samples

In this assignment we are going to look at the limitations the forensic scientists face when collecting evidence to use when prosecuting criminals, we will also look at some of the advantages and disadvantages that are commonplace and we will critically analyse and debate these.

There are infinitely many disciplines to which a forensic investigator can devote his time and interest, traditional fields of study include examination of physical evidence such as firearms, fingerprints and basic psychology. Now however, with advances in technology, relatively new areas of interest to forensic experts are showing their usefulness to investigators, these areas include DNA examination and other chemical analyses, psychological profiling, and the oft-neglected forensic aspect of botany. Each of these sources of information can provide essential clues to investigators and it is important to take advantage of every potential aid in any forensic investigation.

Deoxyribonucleic acid (DNA) is found in all cells, except red blood cells. DNA is said by some to be unique to all but identical twins. However the fact, (crucial for any understanding of DNA evidence), is that there is “no scientific proof of such uniqueness” Findlay, Grix (2003). A crime scene sample is taken either by swab or by collecting an exhibit for sampling. The exhibits and/or swabs are then transferred to a government analytical laboratory where the swab is processed. A whole exhibit is examined visually and samples taken from the areas where it is presumed that DNA might be found. These samples and crime scene swabs are then tested to see if it is possible to determine the type of material found, for example, blood, semen, skin or saliva. “It is not always possible to determine the type of material. Sometimes only a presumptive test can be done” Findlay, Grix (2003)

Forensic investigators are faced with huge workloads on a daily bases with an extremely small window of time to accurately interpret evidence at any scene of crime. As each day passes and without conclusive evidence from forensic experts or their thoughts on the case, the chances of determining crucial and scientific conclusions about the crime are drastically reduced and there is a risk that the evidence would not stand-up in court. For this reason, it is very important to each investigation that the investigators have specialised skills in a specific field of study. This way by having a team of highly trained and focused individuals in their own fields, investigations can be executed as quickly as possible because each forensic scientist thoroughly understands the subject that they are responsible for.

Another factor that can increase the investigation's results is having a number of different forensic specialists on each investigatory team. A group of experts can then produce more answers to any questions that may arise in any particular case that the team has been assigned to. They will be able to determine more based on the various types of evidence, which can then add to the investigators' chances of accomplishing their goals in identifying the victim of the crime, the suspect of the crime, or, perhaps the circumstances surrounding the particular crime.

Forensic botany is the study of plants, and plant matter, as they pertain to criminal death investigations. Forensic botany can provide clues as to when a person died by giving investigators a time frame in which approximations of time of death can adhere to. Having an estimation of estimated time elapsed since death can allow investigators to include and exclude suspects, determine whether or not the case is of current forensic interest and give information on how the person died. Palynology, a sub-discipline of botany, can also provide information about whether a body has been moved since death and where the body has recently been, this data can then be used to support or contradict witnesses and possibly, any suspects statements, or perhaps lead investigators to the actual scene of the crime, as opposed to the place where the body was found. While the use of forensic botany in investigations has proved to be extremely rewarding as far as offering more information about a particular set of circumstances, it also has certain limitations that must be respected. The study of plants as they relate to forensic issues is being relied upon more and more as it consistently demonstrates itself to be beneficial to death investigations.

 One of the most practical uses of forensic botany is to learn how long a body has been laying in a particular spot Kerley, (1978). Dendrochronology, the counting of the rings in a root, has been a popular choice for determining when a body was buried, if for example the ground around where the body was found has been shown to have been disrupted when the body was buried, it can be assumed that any new growth began approximately when the body was buried Quatrehomme et al., (1997). By counting the number of rings in the new growth, a date, within a year, can be acquired Vanezis et al., (1978), along similar lines, if a plant that is in place when the body is buried is damaged,

"It is, in fact, possible to count the number of annual rings that have been formed since the injury" Quatrehomme et al., (1997)

Thereby giving investigators an estimated elapsed time since the burial. Finally, by studying the length and size of roots found in a burial site, an investigator can rely upon independent data that approximates average root growth for the same plant and apply it to the roots found at the grave Quatrehomme et al., (1997). In essence, a pre-determined mathematical constant describing the rate of growth for a particular root would be entered, along with the length of the actual root, in a formula, resulting in the number of days, weeks or years that the root has been growing, this then relates to the number of days, weeks or years that the body has been present at that particular site. The advantages of studying roots in a forensic sense can thus focus an investigation as to approximately when a body was first placed in a certain grave, saving investigators' time and allowing them to turn to other important tasks. Forensic Palynology "is the science of deriving evidence for court purposes from pollen and spores."Horrocks et al.(1998), Pollen is the male gametophyte released by plants in order to fertilize and perpetuate the plant's species, extremely light and often airborne pollen can be found nearly everywhere, often referred to as a ‘pollen rain,' meaning that pollen is constantly falling from plants and moving by way of the wind.

Because no one can shield themselves from this pollen rain, people carry vast amounts of it on their clothing in their hair and on their skin without being aware of it. As well as a result of differing pollen-producing vegetation in any two areas, the pollen found on a person in one area will be different than the pollen found on the same person in another area. This final point is of interest to forensic palynologists, as each person unknowingly and unavoidably carries pollen evidence on his person showing where he has recently been.

If a body is found near a particularly rare pollen-producing plant, it is possible and likely that the killer has this same pollen on themselves, or the clothes he was wearing at the time of the attack or burial. Because the type of pollen is rare, the pollen evidence could place a suspect at the scene of the crime. Again as a result of the many different types of pollen falling at any particular time, areas have different combinations of pollen which, when found on a suspect produce further evidence that he has been at the scene of the crime. Through extensive research, Horrocks et al (1998), were able to show that different areas which seem to contain similar vegetation to each other, in fact differ "significantly from those of other areas of similar vegetation type" Horrocks et al. (1998) a conclusion which further places a suspect at the exact scene of the crime. Assuming that the palynologist can prove that those particular pollen seeds from the scene of the crime or burial match, or are similar to pollen found on a suspect, the finding of differing pollen in the same specific and unique combination, is an extremely effective and condemning piece of evidence that can be used against a suspect.

As with almost all tools used by forensic investigators, forensic botany does have limitations that must be considered when used in a death investigation. An incorrect conclusion by a forensic team could have severe results as the experts change their focus to support a previous wrong outcome. In a death investigation, where the people's safety could be threatened by a criminal who has not been caught, one can appreciate that all results turned up in the investigation must be valid. The problems with Palynology are unfortunately quite similar to the benefits. As pollen rain covers both the suspect and victim at the scene of the crime and burial site, it is also falling on important evidence. When a piece of evidence is extracted from the ground extreme caution must be taken to cover it immediately as pollen from the scene begins to contaminate it. The more pollen that falls upon this evidence the more difficult it becomes for investigators to determine, whether the pollen was there at the time of death, or when the evidence was recovered.

Although it seems to be a more certain way of learning about a particular crime there are a number of different problems in associating time of burial to plant roots. Quatrehomme et al, were able to isolate several matters that make investigators' tasks even more difficult as they searched for answers. While counting the number of rings in a plant to learn how long that plant has lived, and therefore, how long it has been since the soil was been disturbed, it has been proven that false and incomplete rings do occur Quatrehomme et al. (1997). An extra, false ring or a distorted ring can greatly affect an investigation, and because it is impossible to account for these anomalous rings, simply counting the rings of a root provides only a vague idea of the plant's age.

Because plant matter on a body does not necessarily correspond to the length of time the body has been there, investigators must be aware that they may be looking at older or newer plant growth from when the body was buried Quatrehomme et al. (1997). It is possible that an older, more fully developed plant will take over the younger vegetation. In this struggle of nature, the older plant may grow over the grave, confusing an investigator's analysis of the scene as he wrongfully presumes this developed plant to be the youngest plant. Similarly, if the body is covered at the time of burial, some of the original plants may be replaced over the body Quatrehomme et al. (1997), again giving the investigator a false impression of the scene, as the plant he looks at has been at the scene longer than the body below. Opposingly at the other end of the scale "decomposition must first reach a certain stage before roots can penetrate areas of skin loss on the cadaver" Quatrehomme et al., (1997), this could cause a plant younger than the time of burial to be present at the surface, as its growth has been delayed by the body's rate of decomposition. The limitations of forensic botany are extremely important to investigators, but they do not contradict the aid that forensic botany offers to forensic teams. At this stage, "forensic botany is a valuable tool that deserves wider use" Bock et al. (1997). As each new study is completed outlining the advances that have come from botany and their relation to criminal investigations, it becomes apparent that forensic anthropology has much to gain from this field of study.


We have only looked at a few samples of forensic science and the impact they can have in the court room and how they help investigators in solving crimes of all types, we have seen how forensic science has developed since the very first use in the 6th century and how it will continue to develop over time. So to answer the question of this assignment, what are the problems or limitations surrounding the use of forensic evidence in court?, I think one of the major limitations is time and due process. As with all crime scenes the longer they are left the more evidence is lost and the chances of formulating any conclusions become more difficult. Another problem with forensic science is the chain of custody. If this is not kept then the risk of contamination of evidence will fail when the case is processed in court another limitation forensic science faces is the lack of knowledge and understanding that the members of the jury have when the forensic scientists are explaining how they have come to their conclusion and the run of events that have taken place at the crime scene.