Regarding the current resolution, what are some ways plea bargaining in exchange for testimony [PBET] could be considered unjust? It depends, of course, on who's defining justice.
1. From a victim's perspective, PBET sets up inequality among victims.
A victim of one crime--theft, for example--is denied justice so that another victim can enjoy satisfaction. Why should my right to justice be denied so that another's may advance?
Neg response: Inequality among victims is inherent, since victims feel differently or are harmed differently by similar crimes. One person cries out for the life of the murderer; the next offers forgiveness. The state cannot let victims' subjective feelings tip the scales of justice.
2. Prosecutors use plea bargains coercively.
By dangling PBET in front of disadvantaged defendants matched with public defenders, prosecutors become the new adjudicators. Around 95% of federal cases end in a plea bargain. To keep the wheels of justice turning, the state values efficacy over justice, speed over due process.
Neg response: Plea bargaining in general may increase aggressive prosecutorial tactics, but PBET is different. Only defendants "in the know" can take this route--and if they're "in the know," chances are, they're guilty of something.
3. PBET rewards "guilty knowledge."
A criminal acting in concert has an extra "out" that a criminal acting alone can't employ, thus creating inequality in punishment. Testimony pleas in the U.S. lead to greater sentence reduction than mere plea bargains.
4. And now for a little dubious math.
On the Neg side, a plea bargain might lead to a utilitarian maximization of justice. With no plea, Defendant A (theft) has a 90% chance of conviction, or .9 Justice Points. With no plea, Defendant B (murder) has a 30% chance of conviction, or .3 Justice Points. Total Justice Points: 1.2
With a plea, though, Defendant A accepts a 30% reduction in sentencing (.7 JP) to inform on B, who now has a 90% chance of conviction. Total Justice Points: 1.6
Justice is easy. You just need the right calculator.
5. Other purported benefits of plea bargaining (in general). From a paper by the Passaic County Prosecutor [Word file]:
The plea provides a means by which the defendant may acknowledge guilt and manifest a willingness to assume responsibility for his or her conduct. Pleas to lesser offenses make possible alternative correctional measures better adapted to achieving the purposes of correctional treatment and often prevent undue harm to the defendant from the form of conviction. Also, pleas make it possible to grant concessions to a defendant who has given or offered cooperation in the prosecution of other offenders.(The last sentence, of course, merely restates what we already know.)