Back spattering is -
The synopsis of forensic medicine & toxicology ; dr k.s narayan reddy ;28th edition ;pg.no. 130 Back spattering is seen in case of contact shot where there is sucking in of blood ,hair,fragments of tissues & cloth fibers several cm. Back inside the barrel .
The negative pressure in the barrel, sucking blood and tissues
Passive agent in sodomy
Gushing of blood from the exit gunshot wound
Gushing of blood due to aerial bleed
Mechanical injuries