Is it true that only prosecutors can 'cut a deal' with criminals?

Question

It's a common trope on US cop/law shows that prosecutors will offer a deal to criminals in exchange for testimony favouring their case.

Doesn't this give an unfair advantage to the prosecution over the defence?

Consider this scenario. A rich husband is found murdered in his home, prosecution think the wife did it. During the investigation it comes to light that the crime was witnessed by a burglar breaking into a house across the street.

The witness doesn't want to testify. His personal best option is to say nothing since any statement he give will provide evidence of his own crime.

If the witness says he saw the wife commit the murder then the prosecution might agree to overlook his burglary in exchange for his testimony.

If the witness says he saw someone else commit the crime, then the prosecution have no interest in his testimony and have no motivation to overlook his burglary. The defense on the other hand will want him to testify, but can't offer him any deal - the best option for the burglar would be to refuse to testify, or if forced to testify then to deny being present.

Have I understood the law correctly? Or can the defence also offer a deal in exchange for testimony? (Or is it possible that American cop shows don't stick to the truth?)

UPDATE - similar questions involving witness immunity all talk about the prosecution being able to offer immunity for statements that will help the prosecution only. What about statements that will help the defence only?

Answer 1

canada

Yes; defence has no ability to offer a deal.

You also ask:

Doesn't this give an unfair advantage to the prosecution over the defence?

It is well known that that lessening the punishment a witness will face might be a motivation to lie. Such witnesses trigger the need for the judge to consider giving a Vetrovec warning (named after the case where the principle originated).

Such a warning is needed for certain "unsavoury or disreputable" witnesses when they provide inculpatory reference. Various factors go into deciding whether such a warning is required, including whether the witness received benefits for cooperation such that there is a risk he is lying to the court.

1. Did the witness have any motive to lie or mislead the court?

2. Did the witness receive benefits for cooperation such that there is a risk he is lying to the court?

3. Did the witness have a long criminal history?

4. Did the witness have a history of lying to or manipulating the police?

5. Was the witness an accomplice with knowledge of the circumstances such that it would be easy to falsely implicate the accused?

6. Did the witness have access to disclosure or other information that may explain his evidence or how it was given?

7. Did the witness minimize his own wrongdoing?

8. Did the witness exhibit selective memory?

9. Did important evidence emerge only after the witness exhausted his memory or after prodding by police?

10. Did new information emerge for the first time at trial despite many previous statements?

11. Was the witness evasive?

12. Was the witness testimony inconsistent with external evidence, particularly objective evidence that has been accepted?

13. Did the witness provide prior inconsistent statements?

14. Was the witness internally consistent: did the witness evidence change in testifying?

15. Upon the application of common sense, is the witness evidence impossible, improbable or unlikely?

The warning should include:

(1) drawing the attention of the jury to the testimonial evidence requiring special scrutiny; (2) explaining why this evidence is subject to special scrutiny; (3) cautioning the jury that it is dangerous to convict on unconfirmed evidence of this sort, though the jury is entitled to do so if satisfied that the evidence is true; and (4) that the jury, in determining the veracity of the suspect evidence, should look for evidence from another source tending to show that the untrustworthy witness is telling the truth as to the guilt of the accused.

Answer 2

united-states

The defense cannot offer a plea deal to another potential criminal defendant, because (in all but a handful of U.S. states, and for all but a small number of offenses even in those states), private citizens can't charge people with crimes.

But, the defense can subpoena a witness to force that witness to testify (this is a constitutional right). And, the prosecution had a duty, called a Brady duty after the U.S. Supreme Court case creating the duty as a matter of federal constitutional law, to disclose exculpatory evidence in its possession (including witness statements) to the defense.

If the prosecution discloses information that the witness has, the defense can compel that witness to testify on the behalf of the defense.

Frequently, the defense can also compel the court to grant the witness use immunity for the compelled testimony if it would be self-incriminating, preventing the witness from claiming a 5th Amendment privilege when providing the subpoena compelled testimony.