Bloodstains at crime scenes can be deposited or projected on many surface types, and the importance of Area of Origin (AO) calculations for impact stains are vital in the sequence of events. In the UK, wallpaper is a common material used to decorate walls. This study looked at the effect different wallpapers had on the calculated Area of Origin (AO) using FARO Zone 3D (FZ3D) software. A variety of wallpaper types were used, such as Foil, Printed, Vinyl, Washable, Woodchip and Anaglypta. These consisted of smooth and rough surface textures while the control was a plain painted wall. For each wallpaper type and control plain wall, six repeated impacts were conducted. An impact rig with a spring tension arm was fixed 45 cm from the X wall and 45 cm from the Y wall, and remained the same throughout the experiment, to resemble an impact blow for a bloodletting event. The location was also known to the analyst. AO error co-ordinates were measured directly in the FZ3D software to the known impact location, and the results were analysed. An overall 30 cm maximum allowable error from the known impact location was chosen since it was expected that textured surfaces would not perform as well. Nonetheless, 30 cm can still distinguish between a person that is low to the ground, kneeling or standing. The mean AO errors for each wallpaper type were Plain wall, 9.77 cm, Anaglypta wallpaper, 18.55 cm, Woodchip wallpaper, 13.99 cm, Washable wallpaper, 9.81 cm, Foil wallpaper, 10.82 cm, Printed wallpaper, 10.77 cm and Vinyl wallpaper, 9.59 cm. The maximum error for any one impact test was 24.81 cm which was within the chosen 30 cm limit. Wallpapers that had highly textured surfaces had the greatest errors. Also, FZ3D is shown to be an acceptable tool when analysing impact bloodstain patterns on different wallpaper types.

INTRODUCTION
In recent years, scientists and law enforcement agencies have been introduced to sophisticated technologies, which assist in bringing criminals to justice or to prevent an innocent individual from being convicted.1 Among the variety of recent additions of technology, experts and jurors see a dramatic change in metrological technologies - the scientific study of measurement. Innovations from forensic science research and development are introducing these new techniques for the purpose of crime solving, and increasing the reliability, efficiency and validation of forensic testing.2 Software packages such as HemoSpat,3 , BackTrack4 and FARO Scene5 have been independently tested, compared and validated through published, peer reviewed scientific articles. In addition, these software packages have been available for many years to allow for the analysis of bloodstains in a digital manner by utilising photographs and measurements to determine the Area of Origin (AO). The AO is defined as the threedimensional area from which impact stains originated. The AO is defined as the threedimensional area from which impact stains originated. The angle at which a blood droplet impacts the surface can be determined by a relationship, first observed by Dr. Victor Balthazard and subsequently formulated by Dr. Conrad Rizer. The angle (θ) is determined by taking the arcsine of the ratio between the width (W) and length (L) of an individual blood droplet, (θ = sin-1 (W/L). Crime scene investigators use this calculation when utilising the traditional stringing method to determine the angle of impact.

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