what is meant by point of impact on a glass surface? with regards to forensic?

Answer 1

The point of impact is where something first hit something else, a good example is a bullet striking a glass window pane.

The energy of the bullet is dissapated when the window is struck - the point of impact will take the majority of the energy from the bullet, the rest of the energy is then shared by the rest of the window.....

This normally appears as radial (rings of) damage around the point of impact - think of ripples in a pond, they form around where an object has been dropped in i.e. the point of impact.

Taken from.....
http://www.fbi.gov/hq/lab/fsc/backissu/jan2005/standards/2005standards7.htm

Concentric cracks are fractures forming in an approximately circular pattern around the point of impact. They are usually in straight segments that terminate in an existing radial crack.

Cone or crater (Hertzian cone) is a funnel-shaped area of damage caused by a high-velocity impact.

Hackle is a line on the crack surface running parallel to the local direction of crack spreading.

Radial cracks are fractures extending outward from the point of impact.

Ream is an imperfection; nonhomogeneous layers of flat glass.

Wallner lines (ridges) are rib-shaped marks with a wave-like pattern. Wallner lines are called rib marks or ridges to describe their shape and are almost always concave in the direction from which the crack was propagating.

Answer 2

The point of impact on a glass surface in forensics is the point at which "the object" hits the glass surface and the glass breaks. If "the object" hits the glass and the glass does not break the point of impact can be estimated. You can usually tell where the point of object is because there are radiating fractures that would surround it. Hope this helps.