The Correlation Study Between Projected Bloodstain Pattern And Jet Diameter As Well As Jet Angle

Objectives : Through simulation experiments,researcher form projected bloodstain,to record and observe the impact of jet diameter and jet angle on the morphological characteristics of projected bloodstain,as well as other objectives include: measure spray distance,statistically analyze the correlation between jet diameter and jet angle,study the relevance between the projected bloodstain pattern and jet diameter as well as spray angle,to provide scientific reference for bloodstain pattern analysis of crime scene.Methods:Establish an indoor experimental environment which as a constant temperature of 25 degree Celsius,and the glazed tiles will be the carrier of the bloodstain.Set up self-control simulated jet system,connect the medical silicone hose,the negative pressure glass bottle with experimental blood,and pointer sphygmomanometer,and then put it on the holder that can be adjusted.To adjust the height to 120 cm,stabilize the direction of the hose,and record the place of hose's exit end.Increase the pressure till the blood fill up the hose and then clip the hose using vascular clamp,continue increasing pressure till 120 mmhg,release the vascular clamp,to form a projected bloodstain.Respectively select 4 different jet diameters and 13 different jet angles in the same vertical plane.Start the spray experiments in sequence,each experiment need to repeat 5 times,record the results using camera.Observe the morphological characteristics of the bloodstain.Measure the straight line distance from the hose' exit end ground correspondence point to tangent of the bloodstain tip(except for the spatter bloodstain)along the spray direction,entry the data using Excel 2010.Jet diameter,and jet angle are independent variable,projection distance is dependent variable,statistically analyze using SPSS 20.0.Results:Projected bloodstained formed by simulation experiments mostly are linear distributed(except for 90 degrees and-90 degrees),with drip bloodstain and spatter bloodstain,and distributed symmetrically from left to right.Its distribution area increases with the increase of the jet diameter.The concentrated bloodstain formed in the upward direction of the jet mostly showed in a straight line,however those concentrated bloodstain formed in the downward direction of the jet mostly showed like spindle shape or similar with exclamatory mark.The drip bloodstain is circular or in oval shape,their edge is smooth,seldom presented with irregular shape at the edge.There are overlapping connections,mostly happened in the front of projected bloodstain and the end of projected bloodstain.There is no significant correlation showed between the diameter of drip bloodstain and jet diameter.There is no significant difference in the diameter of the small drip bloodstain from different jet diameter,however as the jet diameter increase,the bigger drip bloodstain has showed increasing the diameter as well.The spatter bloodstain mostly distributed to irregular radical shape,concentrated in a fan-shape like area,relatively in smaller shape,mostly presented with irregular multilateral shape,long oval shape(or long oval with tail shape)and point shape.With the changes of the jet diameter and jet angle,the distribution area of the spatter bloodstain is enlarged when jet diameter increase,the angle of the fan changes in different ranges.The distribution range and density of three different types of spatter bloodstain changes as well,however the density of the distribution decreases gradually from the concentrated bloodstain to the peripheral remains the same.The statistical analysis of the experimental data shows: The jet diameter and jet angle have interaction with the spray distance.When jet angle is less than or equal to 0 degrees,there is independent positive correlation between spray distance and jet diameter or jet angle.When jet angle is greater than or equal to 0 degrees,jet diameter and spray distance are in independent positive correlation,jet angle and spray distance are in independent negative correlation.Conclusion:The projected bloodstain is related to jet diameter and jet angle.The morphological characteristics of the projected bloodstain that left over the crime scene can be used for the bloodstain pattern analysis,such as distinguishing the projected bloodstain,inferring the bleeding points,judging the sequence of bloodstain formation and so on.Which helps to improve the scientific and accuracy of the bloodstain pattern analysis.