South Dakota is one of only two states in the country that uses the "slight/gross" comparative negligence rule — if your fault is anything more than slight in comparison to the defendant's, you are completely barred from recovery, a standard that is far more restrictive than the 50% or 51% bar used in every other modified comparative fault state.
South Dakota's unique fault standard, combined with a motorcycle culture shaped by the annual Sturgis Rally and wide-open western highway riding, creates a legal environment where the first days after a crash determine everything. Insurers who understand the slight/gross rule will push aggressively to characterize your riding as anything more than slightly at fault — because that characterization eliminates the entire recovery.
SDCL § 15-2-14 gives you three years from the date of injury to file a motorcycle accident lawsuit in South Dakota. But the evidence that determines fault — and therefore determines whether South Dakota's uniquely harsh comparative negligence rule bars your claim entirely — disappears within days. Surveillance footage from nearby businesses overwrites in 24 to 72 hours. Vehicle event data recorder (black box) information must be downloaded before subsequent ignition cycles overwrite the pre-crash recording. Skid marks and debris patterns on the roadway are cleared by road crews and rain. An attorney who moves immediately after the crash can preserve this evidence before it is gone — an attorney retained weeks later often finds only the at-fault driver's version of events and their insurer's carefully constructed narrative.
SDCL § 20-9-2 codifies South Dakota's "slight/gross" comparative negligence rule — one of the most plaintiff-restrictive fault standards in the country. South Dakota and Nebraska are the only two states that still use this system. Under the slight/gross rule, you recover only if your negligence was "slight in comparison" with the defendant's negligence. "Slight" is a qualitative standard, not a percentage, and South Dakota courts have construed it strictly. If your fault is characterized as more than slight — even 15% or 20% in other states' terms — you may be completely barred from any recovery. This is dramatically harsher than the 50% bar in most states, where a rider who is 49% at fault still recovers. In South Dakota, a rider the insurer can paint as even marginally inattentive may lose everything.
South Dakota's partial helmet law under SDCL § 32-20-4 requires helmets only for riders and passengers under 18. Adults 21 and older may legally ride without a helmet. But in a personal injury lawsuit governed by the slight/gross rule, the defense will argue that not wearing a helmet increased the severity of head or facial injuries — and under SDCL § 20-9-2, even a modest contribution of the rider's conduct to their own damages could tip the fault characterization past "slight" and bar the entire claim. A rider who was wearing a DOT-certified helmet removes this argument entirely. For all other riders, the defense's ability to introduce helmet non-use evidence under the slight/gross framework makes the South Dakota comparative fault analysis uniquely high-stakes.
Lane splitting — riding between lanes of moving traffic — is explicitly prohibited in South Dakota under SDCL §§ 32-20-9.1 and 32-20-9.2, which require motorcycles to use the full width of a single lane and prohibit overtaking vehicles in the same lane. If an insurer can establish that the rider was lane splitting at the time of the crash, that conduct will be characterized as more than "slight" negligence under the SDCL § 20-9-2 standard and the entire claim will be barred. Even when the rider was not splitting lanes, insurers routinely investigate lane position and will use any ambiguity in the collision geometry to suggest the rider was operating outside their lane. Traffic camera footage, witness statements, and road geometry analysis preserved immediately after the crash are the primary tools for demonstrating the rider was properly positioned.
Legal Information Notice
The legal information on this page is for general educational purposes only and is not legal advice. Laws change, and every case is different. Always consult with a licensed attorney in your state to verify the current law and how it applies to your specific situation.
SDCL § 20-9-2 applies the "slight/gross" comparative negligence standard — one of only two states in the country that uses this system. You recover only if your negligence was "slight in comparison" to the defendant's. This is far more restrictive than the 50% or 51% bar in most states. Even a relatively minor contribution to the accident — not watching for a turning vehicle, riding at the speed limit in a way the defense characterizes as too fast for conditions — can be argued to exceed "slight" and bar the entire recovery. The slight/gross rule is why South Dakota motorcycle cases require aggressive, early evidence-gathering that establishes the defendant's fault overwhelmingly. Source: South Dakota Legislature, https://sdlegislature.gov/api/Statutes/Statute/20-9-2
SDCL § 15-2-14 provides a three-year statute of limitations for personal injury claims. However, the evidence that proves fault — and determines whether the slight/gross rule bars your claim entirely — disappears in days: surveillance footage within 24-72 hours, black-box data within days of subsequent ignition, roadway evidence within hours of the first rain or road crew response. If a government road defect or government vehicle contributed to the crash, SDCL § 3-21-2 requires a written notice of claim within 180 days of the injury. Missing the 180-day notice deadline permanently bars the government-entity claim even if the three-year civil SOL has not expired. Source: South Dakota Legislature, https://sdlegislature.gov/api/Statutes/Statute/15-2-14
SDCL § 32-20-4 requires helmets for operators and passengers under 18. Adult riders 18 and older are not required to wear helmets. Violations carry a Class 2 misdemeanor classification. However, not wearing a helmet is directly relevant to South Dakota's comparative fault analysis under the slight/gross rule — the defense will argue that helmet non-use contributed to head injury severity, and under SDCL § 20-9-2, even modest rider fault attributions can bar the entire recovery. A rider wearing a DOT-certified helmet eliminates one of the most common defense arguments used to characterize rider fault as more than "slight." Source: South Dakota Legislature, https://sdlegislature.gov/Statutes/32-20-4
No. SDCL §§ 32-20-9.1 and 32-20-9.2 require motorcycles to use the full width of a single lane and prohibit overtaking vehicles within the same lane. Lane splitting is illegal in South Dakota. Under the slight/gross comparative fault rule (SDCL § 20-9-2), if an insurer can establish that the rider was lane splitting at the time of the crash, that conduct will almost certainly be characterized as more than "slight" negligence — barring the entire claim. Even when the rider was not splitting lanes, defense teams investigate lane position and use ambiguous crash geometry to suggest improper lane use. Source: South Dakota Legislature, https://sdlegislature.gov/Statutes/32-20-9.1
South Dakota does not cap compensatory damages in personal injury cases. Available recovery includes past and future medical expenses, lost wages and earning capacity, rehabilitation costs, pain and suffering, disability, and property damage. The critical obstacle is South Dakota's slight/gross comparative negligence rule (SDCL § 20-9-2): if the defense successfully characterizes the rider's fault as anything more than "slight," the entire recovery is eliminated. Punitive damages are available in South Dakota when the defendant's conduct was oppressive, fraudulent, or malicious. The minimum auto insurance requirement is $25,000/$50,000/$25,000 under SDCL § 32-35-70, and serious motorcycle crashes routinely exceed these floors — making UIM coverage investigation essential. Source: South Dakota Legislature, https://sdlegislature.gov/Statutes/32-35-70
All legal information on this page is sourced from primary government statutes. Last verified 2026-04-07.
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