The Study of Blood Splatter in Crime Scenes, Research Paper Example

Abstract

This paper examines the study of blood splaater in crime scenes.  How specialists in forensics and criminology use this technique to obtain clues of a crime.  Consideration is made of the history in the development of this technique and its use in a modern setting.  The paper is split into four distinct parts (1) Background (2) Historical significance (3) Use in Criminal Investigations and (4) Conclusion.  Is the technique still a valid part of criminal investigation today and how might the science develop?

Background

Blood Spatter models are essentially 3-D mapping depictions of a crime scene. It links to the importance of post mortems in crime scenes in order to find vital clues and evidence that may lead to the arrest of the perpetrator of the crime. Amongst the forensic examinations is that of looking at blood stains at the scene of the crime. This is accomplished by taking pattern analysis from varying blood spatters that may occur in such places as the floor, walls, furniture etc. The investigations use elasticated string which they pin to the stain in order to determine the angle of impact.

Historical Significance

Historically this approach has suffered from a lack of accuracy, as the blood travels similar to that of a bullet i.e. it curves or bends with velocity and as such makes the precise angle of impact difficult to predict. This challenge was met by two Swiss Research Scientists from the University of Bern ( Ursula Buck and Silvo Natter) who have developed a new 3-D modelling system that provides “ a more accurate reconstruction of a crime scene” (Marks, 2010).

The research team first used a laser scanner to create a 3-D digital image of the crime scene. This was accomplished with the use of a digital camera to record the actual shape of the blood stain. Another laser device referred to as a ‘tachymeter’ is used to determine the precise location of the blood stain for plotting on the digital 3-D image model. From the initial information the team calculates the mass of the blood from the size of each stain. Sophisticated software in the computer can then determine the trajectory in reverse and as such the origin of the blood spatter. “The 3D results give us good clues about the area of origin, the number of blows, the positioning of the victim and the sequence of events,” says Buck. The system has already helped in two murder inquiries, revealing in one that a woman killed by her husband was lying in bed rather than sitting up when attacked.” (Marks, 2010).

One UK Scientist has endorsed the usefulness of this approach but equally stressed the importance of human forensic expertise at the scene of the crime “”This seems a useful way to capture 3D blood pattern information,” says Gillian Leak, a blood pattern analyst with the UK Forensic Science Service in Birmingham. But she adds that there is no substitute for human expertise at the scene of a crime: “You still need a scientist to go into the crime scene to interpret which blood stains are the most important” (Marks, 2010).

Use in Criminal Investigations

Analysis

When getting the bloodstain for analysis, it is examined in the context of the contact and collapse phase. Patterns are framed by the displacement of the blood stains and dispersion of the surfaces that it comes into contact with. These are often seen to form the shape of an ellipse. Mathematics using linear least squares and other problem solving equations are used to create complex algorithms that define further information about trajectory and the distance the blood was conveyed to the scene of the crime. Calculations need to be made that cover such items as “droplet speeds, mass, density impact angle and the surface upon which the blood lands” (A.R. Shen, 2005). The information obtained by these calculations may then be illustrated in graphical format showing actual vs. computed angle of impact. In the illustration here it was show with droplets of water being dropped from 20cm and 40 cm of height. Similar experiments were based upon using photographed or scanned images of paint stains. “While both are imperfect compared to the true angles, they are very close to each other, indicating that hand-held photography of blood spatter may not adversely affect our algorithm.” (A.R. Shen, 2005).

Forensic science benefits from this approach by “the speed at which the blood contacted the surface can be approximated. This can help distinguish, for example, between the rapid movement of blood that can be produced by a gunshot or the severing of an artery in opposition to the slower movement of blood from a minor cut.” (Lerner, 2006).  One of the first things that the forensic scientist must do is to determine if the blood is really of human origin, hence “determined by using tests that are portable enough to be used right at the scene. Later, tests will be done to determine if the blood is animal or human in origin and even to narrow down the people from whom the blood may have come.” (Lerner, 2006).

The science by which the forensic scientists analyse the blood patterns include key elements such as path direction, impact angle of elevation, the length and width of the stain and the volume or mass of the stain. “Police often want to reconstruct the exact position where the injury occurred.” (Carter, 2010).

Building Evidence

Forensic Scientists assist the police investigation team in building up the body of evidence from the crime scene.  It is possible to determine a number of factors from the disposition and location of blood spatter at a crime scene. For example: the movement of the victim in relation to the assailant, the direction from which the attack came, the object used in the attack e.g. gun, knife, blunt instrument etc., the kind of impact the victim received and a definition of the item that created the wound and the number of times the blow was inflicted.

This type of information or evidence can be corroborated by statements taken from suspects or witnesses.  “There have been many occasions in which a perpetrator asserts that the victim’s death was accidental, but blood spatter analysis contradicts his claim.”  (Castillo, 2010).  Criminals have been known to try and wipe down and cleanse crime scenes in order that forensic experts cannot do their jobs. Nevertheless, even the most minute drop of blood can be revealed by chemical agents “Luminol, a chemical reagent that reacts with the protein haemoglobin found in blood, can reveal even the minutest traces of blood. This chemical causes blood to fluoresce, or glow, with a bright green color.” (Castillo, 2010).

Conclusions

There is no question that Forensic Science continues to play a most vital part in police investigations today.  In addition, the development of technology continues to enhance the importance and capability that this plays in criminal investigations and the criminal justice system. The forensic examinations may be used in any criminal case but are most commonly observed in cases of homicide, rape, and arson. Another key person using forensic science is the medical examiner and it is this person that places the verdict on the person’s death. “Medical examiners employ forensic science to determine the cause of death. Sometimes, the determinations of the medical examiner can show that a victim died of natural causes or by something other than a defendant’s hand. This evidence can literally be a lifesaver to a person facing a homicide charge” (Baker Associates, 2009).

The importance of forensic science is that it provides a quantifiable way in which to solve crime and provide a foundation built upon a solid evidence base. This type of presentation of evidence is a powerful means to convince juries in the guilt or innocence of a person charged with a criminal offence such as rape or murder. The science also removes prejudice and forces investigating teams to concentrate on the body of evidence that is available.

Forensic science helps in the concept of ‘absolute proof’ and the elimination of ‘reasonable doubt’ particularly in murder or homicide cases. In addition to blood spatter we now have DNA testing that can be used in conjunction with this. Each person has a unique DNA fingerprint and from blood samples we are able to determine those persons at the scene of the crime.  The applications of forensics in science continue to develop with the pace of technological advancement.  The ability to link DNA testing with that of blood spatter analysis further re-enforces the investigative analysis capability around crime scenes.

The main advantages derived from blood spatter analysis are that the investigators can determine the direction from which the blow came.  The actual proximity of the bloodstain to the victim, at the crime scene, may assist in the determination of the impact of the blow and subsequently the type of weapon that was used in the attack.  The investigators are also able to obtain an understanding of the number of blows afflicted and the potential locations of the victim and the attacker at the crime scene.  This provides a considerable and powerful body of evidence that may be used in subsequent court or trial cases.

Despite the technology that can now support forensic analysis, it is still not a desktop activity and it is important that most of the investigatory work is conducted at the scene of the crime.  Digital photography has helped considerably in gaining accurate and detailed images of the pictorial evidence at the scene of the crime and assisted later laboratory analysis.

Works Cited

A.R. Shen, G. B. (2005). Toward Automatic Blood Spatter Analysis in Crime Scenes. Cambridge UK: University of Cambridge.

Baker Associates. (2009, 3 30). The Importance of Forensic Science in the Criminal Justice System. Retrieved 10 15, 2010, from Baker Associates: http://www.tennesseecriminallawyerblog.com/2009/03/the_importance_of_forensic_sci_1.html

Carter, F. (2010). Blood spatter analysis. Retrieved 10 15, 2010, from Blood spatter analysis: http://home.iprimus.com.au/ararapaj/craigslea_testbed/Forensic%20Web%20Test%20Site/blood_spatter_analysis.htm

Castillo, F. (2010). Forensic Blood Spatter Analysis – Stains And Spatter From Blood. Retrieved 10 15, 2010, from ezine: http://ezinearticles.com/?Forensic-Blood-Spatter-Analysis—Stains-And-Spatter-From-Blood&id=934816

Lerner, K. L. (2006). “Blood Spatter.” World of Forensic Science. Retrieved 10 15, 2010, from e-notes: http://www.enotes.com/forensic-science

Marks, P. (2010, 7 21). Blood Spatter Model to help crime scene investigation. Retrieved 10 15, 2010, from I09: http://io9.com/5592320/blood-spatter-model-to-help-crime-scene-investigation