Substantial Factor Test

When multiple causes exist, defendant is liable if conduct was a substantial factor in harm.

Representative cases

• O'Grady v. State. 140 Haw. 36 · Hawaii Supreme Court
• Tracy Windrum, Individually, and on Behalf of Her Minor Children, B.W., J.W., and H.W. v. Victor Kareh, M.D. Texas Supreme Court
• Farook W. Taha, D. O. v. Stephanie Blackburn, Individually and on Behalf of All Wrongful Death Beneficiaries of the Estate of Jose G. Lazalde Texas Court of Appeals, 8th District (El Paso)

Related Causation & Damages rules

• Cause in Fact (But-for)But-for causation requires plaintiff’s injury would not have occurred without defendant’s conduct.
• Alternative LiabilityWhen multiple negligent defendants and uncertainty about cause, burden shifts to defendants to disprove causation.
• Proximate CauseDefendant liable for harms that are foreseeable results of negligent conduct.
• Intervening CausesForeseeable intervening acts do not break causation; unforeseeable superseding causes do.
• Thin Skull RuleDefendant takes plaintiff as found and is liable for full extent of harm.
• Damages RequirementNegligence requires actual damages; nominal damages unavailable.
• Comparative NegligenceNegligence damages reduced by plaintiff’s percentage of fault.
• Contributory NegligenceContributory negligence is a complete bar unless last clear chance applies.

Part of Torts on Core Legal Rules — foundational MBE-tested principles with primary-source citations.