Research Paper on Blood Spatter Interpretation

Introduction

Often the difference between succeeding and failing by a crime scene investigator is purely depended on recognizing and the corresponding examination of physical evidence and the final analysis of the same (Akin, 2005). Crime scene investigators can find a wealth of information and evidence at the scene, such as blood stains and spatter. Blood spatter usually examined to identify patterns, the size of the stain, where the stain is located and even the shape so that they can help to give a general picture of what happened and the sequence of events. Interpreting the blood spatter data that is collected from the crime scene is, therefore, a vitality in reconstructing scenes of crime (Bevel & Gardner, 2008; Dutelle, 2011; Brodbeck, 2012, 57).

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Bloodstain Pattern Analysis

Examination of blood stains and their interpretation is premised on the fact that that stains and the pattern they show characterize forces through which they were formed. Therefore, every stain will have a characteristic of the forces that have been applied on them. Such forces may come in form of footprints, weapon used, and many other objects (Freeman & Gerbis, 2008).

The Pattern of the Blood Spatter

Subjecting a source of blood to a greater force than gravity results in blood loss which can for spatter patterns (Brodbeck, 2012, 54). Depending on what amount of energy is applied, the pattern formed will vary accordingly. Another factor that determines the pattern of the stain is the speed with which the blood leaves the body. Blood leaves the veins at different speeds depending on the severity of the inflicted injury (Akin, 2005; Forensicsciencesimplified.org, 2018).

Blood Properties Important to Spatter Analysis

Blood has a high surface tension which is characterized by a contraction to assume a small spherical shape (James, 1998; Freeman & Gerbis, 2008). Therefore, when the blood is spilled, it forms a pattern which is characteristic of how it fell to the surface. The texture of the surface will determine how the stain will look like. Materials such as carpets distort the pattern as the blood sips through whereas hard surfaces such as glass will be more explicit with satellite sports visible (Hakim & Liscio, 2015, 410; BloodStain Tutorial, n.d.).

General Bloodstain Categories

Drip Stains

These are stains that result from gravity acting against the liquid form of blood. They are usually found on the floors and objects lying below the preceding initial blood origin (de Bruin et al., 2011, 1476).

Transfer Stains

Transfer blood stains as the name suggests are as a result of contact between a bloodied surface and an object or body. The stains contaminate surfaces through swiping, contact bleeding and wiping (Brodbeck, 2012, 56; Cho et al., 2015, 233).

Spatter Patterns

They result from blood being subjected to considerable forces than the force of gravity.

Factors Affecting Blood Spatter Pattern

The Direction of the Stain

Generally, blood drops are spherical, and when they fall on a surface at 90 degrees, they form a circular shape with a uniform radius. However, if the angle at which the blood hits the surface is reduced an elliptically shaped stain will result having tails in the travel direction and eventually will start forming satellite stains emanating from the original stain (Attinger et al., 2013, 375; BloodStain Tutorial, n.d.; Connolly et al., 2012, 233).

Experts use this phenomenon in mathematically determining the impact angle. Using the formula

SIN< = width / length

< = invsin (width / length)

The angle obtained is the one from which the droplet originated relative to the plane on which it landed (Connolly et al., 2012, 233).

Determining the Area of Convergence

When experts have determined the direction of travel of blood droplets, they can then use this information to find the convergent area, origin (Forensicsciencesimplified.org, 2018). Lines are drawn the axis of each stain, and the point where they converge is determined (de Bruin et al., 2011, 1476; Buck et al., 2011, 22). The above information coupled with the calculation of angles of impact can help to determine a 3-dimensional area of origin. Software programs such as Hemospat and BackTrack have recently been developed to aid in analyzing blood spatter (Raymond, 2010; Peschel et al., 2011, 257).

Interpretation of Blood Stains

The correct interpretation of blood stains can point investigators in the right direction from which they can seek further evidence (McEwen & Regoeczi, 2015, 1189). It is, for instance, possible for investigators to determine if an object is missing from the crime scene solely depending on blood spatter pattern (Yen et al., 2003, 132; Laan et al., 2015, 11461). They can, therefore, focus their attention if finding the object which can thus help them find the suspect. Another use for bloodstain interpretation is refuting or collaborating assumptions, witness statements, and victim statements (Hakim & Liscio, 2015, 409; Sinke, 2018). If the pattern of the blood spatters is consistent or not with the statement issued then, the investigators can determine the credibility of the witness and can even point them to suspects (Chisum, 2006, 63; Raymond et al., 1996, 161).

Evidence of movement and struggle during and after the crime can be determined from the blood spatter analysis. Investigators can quickly determine whether the victim died instantly or the death in a delayed manner (Attinger et al., 2013, 378). Armed with such information they can them be able to associate the murder to an expert or otherwise. Presence of blood over a wide area such as through the bedroom and sitting room of a house is a clear indication of violent deaths and amateur work. Stains can also show the movement of the individuals after the commissioning of the crime (Karger et al., 2008, 15; Brodbeck, 2012, 51; Hakim & Liscio, 2015, 410).

Information about the injuries which can be obtained from the blood spatter include the number of blows and the sequence with which the wounds were inflicted (Shen et al., 2006). For example, an investigator can determine from the blood spatter on walls, the number of strikes that occurred if the victim was stabbed or cut by a machete inside a house (Eckwert & James, 1998; Illes & Boues, 2011, 4, Freeman & Gerbis, 2008, 2). Patterns of blood drying determine the amount of time since it was spilled. This drying can help in the determination of the length of the assault and which wounds were inflicted first. However, actual clotting is affected by environmental factors, the amount of blood and surface type. Clotting of blood can also help to estimate the period elapsed since the crime took place (Attinger et al., 2013, 385; James et al., 2005).

The type of weapon used to commit a crime can easily be identified by analyzing a crime scene. Blood spatter caused by bullets, for instance, would have both the back spatter at the point of entry and the forward spatter, in case of exit wounds (McEwen & Regoeczi, 2015, 1192; Sinke, 2018; Comiskey et al., 2016, 32). However, even gunshot spatter vary depending on the gun's caliber, the distance between the weapon and victim and relative distance of the victim to the adjacent objects (Buck et al., 2011, 22; BloodStain Tutorial, n.d.; Hueske, 2005).

Some of the crime scenes are due to murder cases and most of the time the victim cannot give a statement and witnesses are not available (Yen et al., 2003, 132; Raymond et al., 1996, 161). In such cases, the interpretation of blood stains can reveal the position of the victim to the assailant. One can determine whether the victim was lying down, seated, or even standing. Other information that may be obtained from the scene includes the height of the assailant to the victim, whether the assailant is left handed or right handed and whether the assailant is a person known to the victim (Attinger et al., 2013, 396; Peschel et al., 2011, 262).

HemoSpat Software

HemoSpat software program was developed with the view to help crime scene investigators in the interpretation of blood spatter at a crime scene. The software does calculations to determine the area of origin for blood stains found in crime scenes (HemoSpat, 2018). The program involves the performance of directional analysis to give insight into the posture of the victim and the location. Unique features present for the use of the software include the ability to select stains, analyzing surfaces that are at an angle, real-time calculation of the area of origin, exporting of data and even documentation of the crime scene ( Hill J, 2017).

The software can automatically detect an ellipse in a blood stain and thus determine the direction of flight of the blood. Furthermore, the analyst has full control and can adjust blood stains as he deems necessary. For ease of viewing the application allows one to change the color contrast between the background and the stain in addition to a quick entry window (HemoSpat, 2018). Also, information about the photos taken is stored automatically such that one can always refer back to determine dates, camera type used and even whether a flash was used when taking the pictures. Other notable advantages include the ability to integrate bloodstain pattern data with other 3D software ( Hill J, 2017).

The software is compatible with systems operating in both Windows and Mac platforms. It works in all Windows systems and Mac (HemoSpat, 2018). The use of the software enables reduction of risks associated with the crime scenes such as contaminating the scene, and health risks. With HemoSpat, costs of crime scene investigations can be reduced such that fewer people access the crime scene and lesser time is taken to find results. The use of the software also tidies up the office because it reduces paperwork and accumulation of photos from crime scenes. However, the machine still cannot replace human expertise which comes along with experience. Some of the scenes need only an expert to figure out what happened (Murray, 2008).

The BackTrack Software

The BackTrack software is a set of programs that uses directional analysis to analyze the location of the basis of the blood drops that moved downwards to leave a stain. The blood source can be accurately be determined by only two out three Cartesian coordinate. The BackTrack system makes it possible for analysts to make use of the digital photographs of the blood stains to calculate the area in space where the source of blood was positioned at the exact time of impact (Illes et al., 2005).

The back track is accurate and efficient in calculating blood drops that move downward to produce stains. Directional analysis by the use of BackTrack software uses the bird's eye view of the flight paths of the drops of blood to calculate the place of the blood source in the floor plane (Illes et al., 2005). At the top view of the flight path the bird's eye looks down on these planes' edges and sees them in straight lines that converge approximately at the location of the source of the blood (Carter et al., 2006, 242).

The advantages of using BackTrack software (Illes et al., 2005).

• Minimizes the risks
• Maximizes the use of information
• Produces precise and reliable results
• Reduced costs
• Takes a shorter time to complete the whole analysis.
• The software uses the latest digital imaging technique.

How the Backtrack Software Works

The blood droplets stains re digitally photographed, then fed into the computer alongside with the data relating to every droplet's X and Y coordinates on the wall. Directional analysis then computes a virtual string for every stain that is a straight line in each stain extending outward 3-D space through a direction that is the same as to the direction of impact of the blood droplet. The analyst c...