Fernando Razo v. State, 01-15-00290-CR

Appellant Fernando Razo was convicted of intoxication manslaughter and sentenced to ten years; he appealed.
Defense theory: concurrent causation — the decedent’s recent marijuana use (per toxicology) caused her unsafe driving and was independently sufficient to cause the collision.
The State filed a motion in limine to exclude any evidence or reference to the decedent’s toxicology/marijuana; the trial court conditionally allowed development only if a qualifying sponsoring witness could be produced.
The forensic chemist who performed the toxicology (F. Shaw) did not testify; Dr. Jeffrey Walterscheid (toxicology co‑director and records custodian) and Dr. Alex John (medical examiner) testified about procedures and effects but the court barred the toxicology report.
The trial court ruled the experts could not develop marijuana/toxicology evidence before the jury: initially as not relevant without the testing chemist, and ultimately excluded the marijuana testimony under Rule 403 as unduly prejudicial and sustained hearsay objections to the toxicology report (business‑records exception rejected).
Appellant argues these exclusions deprived him of his constitutional right to present a complete defense and were reversible error.

Issue	State's Argument	Razo's Argument	Held (as argued by appellant in brief)
Exclusion of decedent’s marijuana evidence under Rule 401 (relevance)	Evidence not relevant without the actual toxicology report/chemist testimony; speculative to infer impairment	Evidence was relevant to concurrent‑causation defense — marijuana use tended to make decedent’s impairment and causation more probable	Trial court excluded; appellant argues exclusion was erroneous because marijuana evidence made his statutory defense more probable
Exclusion under Rule 403 (unfair prejudice)	Even if relevant, probative value is substantially outweighed by potential prejudice and speculation	Probative value high (goes to heart of defense); limited risk of irrational verdict because charge included concurrent causation; limiting instructions could cure concerns	Trial court excluded as more prejudicial than probative; appellant contends Rule 403 balancing was incorrect and exclusion prevented presentation of defense
Exclusion of toxicology report as hearsay (business‑records exception)	Report is hearsay; only person who ran test may introduce it (chemist unavailable)	Lab co‑director/custodian (Walterscheid) supervised, reviewed, and maintained records — qualifies to sponsor under Rule 803(6)	Trial court sustained hearsay objection and excluded the report; appellant argues business‑records predicate was satisfied and exclusion was abuse of discretion

Montgomery v. State, 810 S.W.2d 372 (Tex. Crim. App. 1990) (relevance and Rule 403 balancing; presumption favoring admissibility of relevant evidence)
Holmes v. South Carolina, 547 U.S. 319 (U.S. 2006) (constitutional right to present a complete defense)
Wiley v. State, 74 S.W.3d 399 (Tex. Crim. App. 2002) (exclusion that effectively prevents presentation of defense may be constitutional error)
Potier v. State, 68 S.W.3d 657 (Tex. Crim. App. 2002) (standards for reviewing exclusion of defense evidence)
Moses v. State, 104 S.W.3d 622 (Tex. Crim. App. 2003) (abuse of discretion standard for evidentiary rulings)
Gigliobianco v. State, 210 S.W.3d 637 (Tex. Crim. App. 2006) (definition of probative value and need factor under Rule 403)
Cruz v. State, 122 S.W.3d 309 (Tex. App.—Houston [1st Dist.] 2003) (erroneous exclusion of evidence offered to support a defense)
Kelly v. State, 321 S.W.3d 583 (Tex. App.—Houston [14th Dist.] 2010) (analysis of defense evidence exclusion and constitutional impact)