The u. s. supreme court held that the decision to prosecute may not be deliberately based upon an unjustifiable standard such as race, religion, or other arbitrary classification in:

Bordenkircher v. Haye

Explanation:

In November 1977, Paul Hayes, a repeat offender was accused of forgery which carried a sentence of between 2 to 10 years. The prosecutor offered Hayes a 5-year sentence if he pleaded guilty. Otherwise, he would be jailed for life if found guilty, due to his previous convictions.  

Bringing a charge against offenders and negotiating a plea bargain are within the prosecutor’s discretion. However, when the case was brought before the Supreme court in 1978, it ruled that charges or plea bargains must not be based on “race, religion or other arbitrary classification.”