It serve only one good purpose - that all innocent and less powered people (most people are in this category), fear the police so that keep normal people away from participating in a crime.
Other then the above mentioned implicit good reason, i dont see anything good bout the system.
Why there are no evidence like finger prints on lock, seamen on bed, and so on....what a police..looks like it belongs to 1200BC...only "mouth" they can use, like most of our other great like raj thakere and other use mouth and thats all ...no hardwork ..nothing