*308 OPINION
In these mandamus proceedings, all petitioners challenge orders of the respondent district court granting or denying рretrial motions to disqualify the Clark County District Attorney’s Office from the prosecution of certain criminal proceеdings. We deny the petitions in No. 13900 and No. 13928. We grant the petition in No. 13914.
STATEMENT OF THE FACTS
No. 13900:
Petitioner Collier is charged with murder, robbery with the use of a wеapon, and possession of a firearm by an ex-felon. Collier is represented by the Clark County Public Defender’s *309 Office. When his case first came to the public defender’s office, Thomas Leen was the chief deputy public defendеr. Thomas Leen now works for the Clark County District Attorney’s Office as chief deputy district attorney, but is not participating in Collier’s prosecution.
Collier moved the district court to disqualify the district attorney’s office from prosecuting his case. The district court conducted an evidentiary hearing and thereafter denied Collier’s motion.
No. 13914:
Defendants William O’Donnell, Vicky Ingegneri, and Bernice Cardarelli are charged with selling a controlled substance and conspiracy to sell a сontrolled substance. Defendant O’Donnell is represented by the Clark County Public Defender’s Office and defendants Ingegneri аnd Cardarelli have each retained private counsel.
Defendant Cardarelli moved the district court to disqualify the Clark County District Attorney’s Office from prosecuting the case on the ground that Thomas Leen had formerly representеd co-defendant O’Donnell while Leen was employed at the Clark County Public Defender’s Office. The district court, without holding an evidentiary hearing, granted Cardarelli’s motion, thereby disqualifying the district attorney’s office from prosecuting all three defendants.
No. 13928:
Petitioner Russell Crew, charged with two counts of murder and two counts of use of a deadly weapon in the commission of a crime, moved the district court to disqualify the Clark County District Attorney’s Office from prosecuting his case. He contended that a conflict of interest was present due to Bill Berrett’s position with the district attorney’s office as a deputy. Mr. Berrett, a former private practitioner, had represented Crew’s co-defendant at the co-defеndant’s murder trial. Berrett is not participating in Crew’s prosecution, however.
After holding a hearing on the motion, and reviеwing the briefs and affidavits submitted in support of and in opposition to the motion, the district court denied Crew’s motion.
DECISION
The disqualifiсation of a prosecutor’s office rests with the sound discretion of the district court. Tomlin v. State,
[Ejthical rules require that a lawyer should avoid even the appearance of professional impropriety and that in certain situations the disqualification of one lawyer within a law firm means that all mеmbers of the firm are also disqualified. Canons 5 and 9, DR 5-105(D). While this principle is strictly enforced in the context of civil actions сonducted by private law firms, it is less strictly applied to government agencies. Where a lawyer who has represеnted a criminal defendant on prior occasions is one of the deputy prosecutors, disqualification of the entire office is not necessarily appropriate. Individual rather than vicarious disqualification may be the аppropriate action, depending upon the specific facts involved. (Emphasis added.)
Further, we recognize that vicarious disqualification may be warranted in extreme cases where the appearance of unfairness or imрropriety is so great that the public trust and confidence in our criminal justice system could not be maintained without such аction. Such an extreme case might exist even where the state has established an effective screen prеcluding the individual lawyer’s direct or indirect participation in the prosecution.
Finally, while mandamus lies to enforce ministerial acts or duties and to require the exercise of discretion, it will not serve to control the proper еxercise of that discretion or to substitute the judgment of this court for that of the lower tribunal.
See
Kochendorfer v. Board of Co. Comm’rs,
In petition No. 13900, the district judge, aftеr considering the testimonial evidence presented at the evidentiary hearing, exercised his discretion and deniеd Collier’s motion to disqualify. Similarly, in petition No. 13928, the district judge, after holding a hearing on Crew’s motion to disqualify and reviewing the briefs and affidavits submitted in support of and in opposition to the motion, denied Crew’s motion. Since the respondent district judges in bоth petition No. 13900 and petition No. 13928 exercised their discretion, and since neither Collier nor Crew has demonstrated that the district judges acted arbitrarily or capriciously in doing so, mandamus does not lie *311 to challenge the denial of their motions to disqualify. Accordingly, we deny the petitions in No. 13900 and No. 13928.
In petition No. 13914, however, the district judge granted the motion to disqualify without holding an evidentiary hearing. Additionally, the district judge refused to hear argument from the district attorney. His ruling was based solеly on the appearance of impropriety, rather than a consideration of all the facts and cirсumstances. We find, therefore, that the district judge, in effect, failed to exercise his discretion. Accordingly, we grant a petition for writ of mandamus in No. 13914. We vacate the order of the district court disqualifying the entire district attorney’s office. The district court shall conduct an evidentiary hearing on defendant Cardarelli’s motion, and after a consideration of all the relevant facts, shall determine whether the prosecutorial function can be carried out by the Clark County District Attorney’s Office impartially and without breach of any privileged communication. 1
Notes
We express no opinion on what the outcome of that hearing should be.