If foul play is involved, the best way to dispose of a human corpse would be lye. Lye is a substance also known as sodium hydroxide (chemical formula NaOH) and is used mainly in chemistry labs, and in the production of soap.

The soap-making (and corrosive) property of the chemical is what is most beneficial for our purposes.
Take the corpse, place it in some large garbage bags, and transfer it to the trunk of your car. Then, drive the car to your house, and at night when your neighbors won't see you, transfer the body to your bathtub. Now take the body out of the plastic bags, and strip it naked. It would be a good idea to burn the bags, and the clothes. Cover the body with a whole bunch of lye, plug the tub, and fill with a small amount of warm water.

Less than a week later, pull the plug, and the body will be oh-so-much soap and hair. Now all your legal problems are over.

Disclaimer: Don't fucking do this! Seriously, don't! If you do, it's not my fucking problem or fault