Mont. Code Ann. § 27-1-705

27-1-705 . (Effective on occurrence of contingency) Several liability -- purpose -- pleading -- determination -- nonparties. (1) The purpose of 27-1-703 and this section is to substitute several liability for the former law providing for joint and several liability, except for certain actions. The purpose of several liability is to allocate responsibility based on fault to all parties to an occurrence, rather than only to the parties to the litigation, and to ensure that the liability of each party to an occurrence is allocated in direct proportion to that party's fault.

(2) In an action brought as a result of the death of a person or injury to a person or property, the liability of a defendant is several only and is not joint, except as provided in subsection (7). A defendant is liable only for that percentage of damages that is equal to the ratio of defendant's fault to the total fault attributed to all persons involved in the occurrence from which the action arose, including claimants, defendants, and persons not party to the action. A separate judgment must be entered against the defendant for that amount.

(3) In determining the percentage of fault of persons who are parties to the action, the trier of fact shall consider the fault of persons not a party to the action, based upon evidence of those persons' fault, that is admissible in evidence. Assessment of fault against a nonparty does not subject the nonparty to liability in the action or any other action and may not be introduced as evidence of liability in any other action.

(4) The percentage of fault attributable to parties to the action may total less than 100% if the trier of fact finds that fault contributing to cause the claimant's loss is attributable to other persons.

(5) The jury shall return a special verdict, or the judge shall make special findings in the absence of a jury, determining the percentage of fault attributable to each party and determining the total amount of damages sustained by the claimant.

(6) A defendant shall affirmatively plead comparative fault and identify in the answer or within a reasonable amount of time after filing the answer as determined by the court, each person who the defendant alleges is at fault with respect to the occurrence that is the basis for the action. A defendant who pleads the comparative fault of another has the burden of proving the fault.

(7) Section 27-1-703 applies and this section does not apply to an action arising from an act or omission that violates a state environmental law relating to hazardous or deleterious substances.

(8) Parties whose liability arises from acts or omissions in concert or from acts or omissions arising from an agency or employment relationship must be apportioned a single percentage of fault and must be treated as a single party for purposes of this section.

(9) For purposes of this section, "fault" means an act or omission that proximately caused or contributed to injury or damages sustained by a person seeking recovery and includes negligence in any of its degrees, contributory negligence, strict liability, and products liability.