Acid rain is rainfall made sufficiently acidic by atmospheric pollution that it causes environmental harm, typically to forests and lakes. The main cause is the industrial burning of coal and other fossil fuels, the waste gases from which contain sulfur and nitrogen oxides, which combine with atmospheric water to form acids.
The evidence that we will have to investigate is the gunshot residue on the body of the suspect. When a person fires a gun there will be a deposition of material from the components of the chemicals present in the gun. This deposit is called gunshot residue and consists of particles of the propellant or explosive primer.
Experimentation has shown that the period of time that is person will test possible for gunshot residue is 5.27 days.