Penal Code Section 654, subdivision (a) prohibits both multiple punishment and multiple prosecution, providing in pertinent part: "An act or omission that is punishable in different ways by different provisions of law shall be punished under the provision that provides for the longest potential term of imprisonment, but in no case shall the act or omission be punished under more than one provision. An acquittal or conviction and sentence under any one bars a prosecution for the same act or omission under any other." The prohibition against multiple punishment is designed to ensure that a defendant's punishment is commensurate with his criminal liability whereas the proscription against multiple prosecution is a procedural safeguard against needless harassment and the waste of public funds. (Kellett v. Superior Court (1966) 63 Cal.2d 822 at p. 827.) Kellett v. Superior Court (1966) 63 Cal.2d 822 is the leading case on the application of the statute's bar of multiple prosecutions under section 654. In Kellett, the defendant was standing on a sidewalk holding a pistol. He was charged with, and pleaded guilty to, exhibiting a firearm in a threatening manner. The Supreme Court held that this conviction prohibited a later prosecution for possessing a concealable weapon by a felon arising out of the same facts. It stated that: "When, as here, the prosecution is or should be aware of more than one offense in which the same act or course of conduct plays a significant part, all such offenses must be prosecuted in a single proceeding unless joinder is prohibited or severance permitted for good cause. Failure to unite all such offenses will result in a bar to subsequent prosecution of any offense omitted if the initial proceedings culminate in either acquittal or conviction and sentence." (Kellett, supra, 63 Cal.2d at p. 827.)