Commonwealth v. Mendez, 74 A.3d 256

Defendant Oneximo Mendez was charged with long‑running sexual offenses against a minor; the victim gave birth in 2011 and DNA linked Mendez as the probable father.
Trial was scheduled for September 10, 2012, with the Commonwealth ordered to complete discovery by June 8, 2012.
On August 6, 2012 (after the deadline), the Commonwealth sought leave to provide defense counsel a narrative report summarizing an interview of Dr. Philip Bayliss (and Bayliss’s CV) to explain how a woman might be unaware of a pregnancy.
The trial court denied the Commonwealth’s request to provide the narrative report but said the Commonwealth could call the expert on rebuttal if the defense opened the issue at trial.
The Commonwealth appealed, arguing the court’s order improperly prevented mandatory disclosure of expert opinion and unfairly limited admissible expert testimony the Commonwealth intended to present in its case in chief.
The Superior Court vacated the trial court’s order and remanded, directing the Commonwealth to prepare a Rule 573‑compliant expert report and permitting disclosure/admission consistent with discovery rules and precedent.

Issue	Commonwealth's Argument	Mendez's Argument	Held
Whether the trial court abused its discretion by denying the Commonwealth’s request to provide an expert report/opinion after the discovery deadline, thereby precluding use of that evidence at trial	The court’s sanction improperly blocked mandatory disclosure of an expert opinion; the opinion was necessary to explain the victim’s unrecognized pregnancy and was admissible in the Commonwealth’s case in chief	The trial court’s restriction was a proper sanction for late discovery and limited the Commonwealth to rebuttal to prevent prejudice to the defense	The Superior Court held the trial court abused its discretion: the Commonwealth must disclose expert opinions under Pa.R.Crim.P. 573; the expert testimony was admissible in the Commonwealth’s case in chief to explain promptness/credibility; vacated and remanded with instruction to produce a Rule 573(B)(2)(b) report

Commonwealth v. Boich, 982 A.2d 102 (Pa. Super. 2009) (abuse of discretion standard for discovery/evidentiary rulings)
Commonwealth v. Hanford, 937 A.2d 1094 (Pa. Super. 2007) (defining abuse of discretion for evidentiary rulings)
Commonwealth v. Burke, 781 A.2d 1136 (Pa. 2001) (Brady and Commonwealth disclosure duties include expert opinions)
Commonwealth v. Zook, 615 A.2d 1 (Pa. 1992) (purpose and admissibility standard for expert testimony)
Commonwealth v. Minerd, 753 A.2d 225 (Pa. 2000) (expert testimony about physical/medical aspects of sexual assault victims is admissible and does not usurp credibility determinations)
Commonwealth v. Dillon, 925 A.2d 131 (Pa. 2007) (promptness of complaint evidence is relevant and may be presented in Commonwealth’s case in chief)
Commonwealth v. Thomas, 904 A.2d 964 (Pa. Super. 2006) (discussion of prompt complaint evidence and jury instruction availability)