State v. Patterson, 395 P.3d 543

Defendant Anthony Patterson was convicted by jury of two counts of trafficking oxycodone based primarily on testimony of an undercover narcotics agent (Undercover Agent).
Transactions involved the Undercover Agent and a confidential informant; the informant did not testify. One alleged sale involved exchange of five oxycodone pills for a backpack containing a computer projector.
On cross-examination, Patterson sought to question the Undercover Agent about a prior instance in which the agent allegedly admitted under oath to misrepresenting a police report in a federal preliminary hearing; the State objected and the district court sustained the objection without explanation.
Patterson was sentenced (nine years, suspended to five years probation) and ordered to return the projector; he appealed, arguing improper limitation of cross-examination under Rule 11-608 and other claims.
The Court of Appeals found the district court abused its discretion by excluding the proffered inquiry into the agent’s prior alleged untruthfulness, concluding the evidence was highly probative of credibility, not excluded under Rule 11-403 on the record, and the error was not harmless because the agent’s testimony was critical to the State’s case.
The convictions were reversed and the case remanded; the court did not reach Patterson’s other arguments.

Issue	Plaintiff's Argument	Defendant's Argument	Held
Whether district court erred in excluding cross-examination about a prior alleged untruthful police report by the Undercover Agent	Exclusion was proper because the inquiry was irrelevant and constituted improper impeachment or prior-bad-act evidence under Rule 11-404(B)(1)	Exclusion violated Rule 11-608(B)(1) and Confrontation rights; the alleged admission of untruthfulness was probative of credibility	Reversed: exclusion was an abuse of discretion under Rule 11-608(B); not shown to be excluded under Rule 11-403; error was not harmless because agent’s testimony was critical

State v. Rojo, 126 N.M. 438, 971 P.2d 829 (discretionary review standard for evidentiary rulings)
State v. Tollardo, 275 P.3d 110 (harmless-error standard for evidentiary error)
State v. Balderama, 135 N.M. 329, 88 P.3d 845 (relevance and admissibility principles)
Baum v. Orosco, 106 N.M. 265, 742 P.2d 1 (prior untruthfulness probative of officer credibility)
United States v. Bocra, 623 F.2d 281 (permissible inquiry about prior lies under Rule 608(b) analog)
Gordon v. United States, 344 U.S. 414 (importance of wide-ranging credibility scrutiny when case depends on single witness)
Davis v. Alaska, 415 U.S. 308 (cross-examination as principal means to test credibility)
State v. Samora, 387 P.3d 230 (abuse-of-discretion framework)
United States v. Whitmore, 359 F.3d 609 (evidentiary error not harmless when sole eyewitness prevented from credibility challenge)