Joint and several liability in Illinois works on a tiered system built around a 25 percent fault threshold. When more than one defendant causes the same injury, any defendant found 25 percent or more responsible can be made to pay the entire judgment for non-medical damages. Defendants below that line pay only their proportionate share of non-medical damages. Medical expenses are treated separately: every liable defendant is on the hook for the full amount, no matter how small their share of fault.
The 25 Percent Rule and How Fault Is Measured
The controlling statute is Section 2-1117 of the Illinois Code of Civil Procedure. It applies in negligence and strict product liability cases involving bodily injury, death, or property damage, and it sorts defendants into three categories.
- All liable defendants share full joint and several liability for the plaintiff’s past and future medical expenses.
- Any defendant at 25 percent or more of the total fault is jointly and severally liable for the rest of the damages too, meaning the plaintiff can collect the whole judgment from that one defendant.
- Any defendant below 25 percent is only severally liable for non-medical damages and owes only their proportionate share of items like lost wages, pain and suffering, and property damage.
The threshold calculation is where cases are often won or lost. The statute measures each defendant’s fault against the total fault of everyone involved: the plaintiff, every defendant the plaintiff sued, and any third-party defendants except the plaintiff’s employer.1Illinois General Assembly. Illinois Code 735 ILCS 5/2-1117 – Joint Liability A defendant who looks heavily at fault when compared only to co-defendants can end up below 25 percent once the plaintiff’s own negligence and a third-party defendant’s share go into the denominator.
The medical-expenses carve-out has real consequences. A defendant who is only 5 percent at fault can still be forced to pay the plaintiff’s entire hospital bill. In catastrophic-injury cases where medical costs dwarf everything else, the 25 percent line offers less protection than a defendant might assume.
When the 25 Percent Threshold Does Not Apply
Section 2-1118 removes the threshold entirely in two categories of cases. In those categories, every liable defendant is jointly and severally liable for all damages regardless of fault percentage.2Illinois General Assembly. Illinois Code 735 ILCS 5/2-1118
The first is environmental contamination. Any case where the injury was caused by discharging pollutants into the environment, including hazardous substances, chemicals, radioactive waste, asbestos, and mine tailings, falls outside the 25 percent rule. Response action contractors hired to clean up the contamination are the one exception within this category and still get the benefit of the threshold.
The second is medical malpractice. In a malpractice action based on negligence, every liable defendant is jointly and severally liable for the whole judgment. A physician found 10 percent at fault can be pursued for the entire amount.
How the Plaintiff’s Own Fault Fits In
Illinois follows a modified comparative fault system under Section 2-1116. A plaintiff more than 50 percent at fault recovers nothing. A plaintiff at 50 percent or below still recovers, but the award is reduced by their share of fault. A $500,000 verdict with the plaintiff 30 percent responsible pays out $350,000.3Illinois General Assembly. Illinois Code 735 ILCS 5/2-1116 – Limitation on Recovery in Tort Actions
Comparative fault interacts with joint and several liability in ways worth understanding. Because the plaintiff’s fault sits in the denominator of the 25 percent calculation, a defendant with a middling share among co-defendants can slip below the threshold once the plaintiff’s own negligence is counted. Defense work aimed at shifting fault to the plaintiff can therefore do double duty: it shrinks the total award and it may drop the client out of joint and several exposure for non-medical damages.
Contribution Between Defendants
A defendant who ends up paying more than a fair share is not stuck with the loss. The Joint Tortfeasor Contribution Act, at 740 ILCS 100, lets that defendant seek contribution from co-defendants who caused the same injury. The right exists even when no judgment has yet been entered against the other tortfeasors.4Justia Law. Illinois Code 740 ILCS 100 – Joint Tortfeasor Contribution Act
The rule is simple in principle. A defendant who paid more than a pro rata share can recover the excess, and no defendant can be forced to contribute more than a pro rata share. In practice, contribution claims take time and money and often require proving each co-defendant’s proportionate responsibility in a second round of litigation. Contribution claims must also be filed within two years, and missing that window forfeits the right.
Keep the two statutes straight. Section 2-1117 governs what the plaintiff can collect from each defendant. The Contribution Act governs how the defendants sort out the bill among themselves once the plaintiff has been paid. A plaintiff who collects the full judgment from one deep-pocketed defendant is finished with the case; contribution is a fight between the defendants.
How Settlements Reshape the Case
When one defendant settles, the Contribution Act reallocates the case around that settlement. A good-faith settlement does three things at once.
- The settling defendant is discharged from contribution. No co-defendant can pursue them for contribution later, even if the settlement was for less than a proportionate share.
- The settling defendant loses the right to seek contribution from anyone else.
- The judgment against the remaining defendants is reduced by the settlement amount, or by the consideration actually paid, whichever is greater.
That third piece is the settlement credit.4Justia Law. Illinois Code 740 ILCS 100 – Joint Tortfeasor Contribution Act If the plaintiff wins a $1 million judgment after already settling with one defendant for $400,000, the remaining defendants owe $600,000. The credit prevents double recovery while letting the plaintiff pursue the balance.
The “good faith” label matters. If a settlement is not in good faith, it does not trigger the contribution bar or the automatic credit. Courts look at whether the settlement amount reasonably reflects the settling defendant’s proportionate liability and whether the plaintiff and the settling defendant colluded to disadvantage the others.
What This Means in Practice
For plaintiffs, joint and several liability is a safety net. When one defendant has deep pockets and others do not, the plaintiff can collect the full judgment from the solvent defendant for medical expenses and for non-medical damages where that defendant is 25 percent or more at fault. The risk of an insolvent co-defendant falls on the other defendants, not on the injured person.
That safety net has limits. If every defendant sits below 25 percent individually, the plaintiff can collect only each one’s proportionate share of non-medical damages, and an insolvent defendant’s share simply disappears. The medical-expenses rule remains the backstop: those costs stay fully collectible from any liable defendant.
Plaintiffs in medical malpractice and environmental contamination cases hold the strongest position because Section 2-1118 pulls the 25 percent threshold out of the picture entirely. Every liable defendant answers for the full judgment.
For defendants, the strategic center of gravity is the 25 percent line. Fault shifted to co-defendants, to non-parties, or to the plaintiff can drop a defendant below the threshold and cap non-medical exposure at a proportionate share. Early settlement is another lever. A defendant who settles in good faith walks out with full protection from later contribution claims, which can be the cheaper path when a co-defendant is insolvent and contribution would be uncollectible anyway.