If the identity of the driver is discovered after July 15, 2024, Plaintiffs may move to amend the complaint showing first good cause under Rule 16, followed by the grounds for leave to amend under Rule 15. See Upton v. Corizon Health Care Inc., No. CV-17-01502-PHX-JAT, 2019 WL 581274, at *2 (D. Ariz. Feb. 12, 2019) (“Once the district court has filed a pretrial scheduling order pursuant to Rule 16 which establishes a timetable for amending pleadings, a motion seeking to amend pleadings is governed first by Rule 16(b), and only secondarily by Rule 15(a).”) (cleaned up).

Id. “Federal courts in Arizona and within the Ninth Circuit ‘have articulated and undertaken a three-step inquiry in resolving the question of diligence in the context of determining good cause under Rule 16.'” Upton v. Corizon Health Care Inc., No. CV-17-01502-PHX-JAT, 2019 WL 581274, at *3 (D. Ariz. Feb. 12, 2019) (quoting Morgal v. Maricopa County Bd. of Supervisors, 284 F.R.D. 452, 460 (D. Ariz. June 6, 2012)) (brackets omitted). Those three steps are:

Federal courts in Arizona and elsewhere in the Ninth Circuit have developed a three-part diligence inquiry specific to Rule 16. Morgal v. Maricopa Cnty. Bd. of Sup'rs, 284 F.R.D. 452, 460 (D. Ariz. June 6, 2012) (quoting Grant v. United States, 2011 WL 5554878, at *4 (E.D. Cal. Nov. 15, 2011), adopted by, 2012 WL 218959, at *1 (E.D. Cal. Jan. 23, 2012)); see Upton v. Corizon Health Care Inc., 2018 WL 581274, at *3 (D. Ariz. Feb. 12, 2019). Under this inquiry, courts assess whether the movant (1) diligently assisted the court in creating a workable Rule 16 order; (2) requested to modify the Rule 16 order due to developments that were unforeseeable at the time the order was issued; and (3) was diligent in seeking to amend the Rule 16 order once it became apparent that the movant could not comply.

(1) the party's diligence in assisting the court in creating a workable Rule 16 order; (2) whether the party's noncompliance with a Rule 16 deadline occurred because of the development of matters which could not have been reasonably foreseen or anticipated at the time of the Rule 16 scheduling conference; and (3) whether the party was diligent in seeking amendment of the Rule 16 order once it became apparent the party could not comply.Acosta, 325 F.R.D. at 328 (citing Morgal v. Maricopa Cty. Bd. of Supervisors, 284 F.R.D. 452, 460 (D. Ariz. 2012)); see also Upton v. Corizon Health Care Inc., No. CV-17-01502-PHX-JAT, 2019 WL 581274, at *3 (D. Ariz. Feb. 12, 2019). "Although the existence or degree of prejudice to the party opposing modification might supply additional reasons to deny a motion, the focus of the inquiry is upon the moving party's reasons for seeking modification."