The intersection of straight lines through the long axis of several individual bloodstains in an impact spatter pattern illustrates the of the pattern.

Area of convergence

Explanation:

The area of convergence is the area containing the intersections between the lines and drawn through the axis of the individual stain that is indicated by the two dimensions in the location of the blood source.  

Thus in the above statement, the intersection of lines and long axis in the several individual bloodstains is an impact of spatter pattern which is called the area of convergence.  

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