The decision was reached by the Fourth District Court of Appeal in Riverside in the case in which Karan and Stan Eriksson, owners of a stable in Truckee, are seeking to sue Kristi Nunnink.
The action centres on the death of the Erikssons' 17-year-old daughter, Mia, in a November 2006 eventing competition.
The appeals court overturned a lower court decision that had ruled out the action. The lower court had cited higher court rulings that barred suits over deaths resulting from normal risks associated with a sport.
The latest ruling allowed the action to proceed, noting coaches can be sued for falsehoods that lead an athlete to take greater risks.
In the decision, the court said Mia was an avid horse rider and equestrian competitor, and Nunnink her riding coach.
In November 2006, Mia took part in an equestrian competition at Galway Downs in Temecula.
Although Mia's horse was recently injured in another competition, Nunnink belatedly persuaded Mia's mother, Karan, that the horse, Koryography, was fit to ride in the Galway event, despite the gelding having earlier been injured twice and suffering what a vet considered to be concussion in a fall.
Based on Nunnink's representations, Karan allowed Mia to compete, although her mother said her daughter and riding coach had originally travelled to the event only to watch.
During the cross-country portion of the competition, Mia's horse tripped over a jump. With the Erikssons looking on, Mia fell off the horse and the horse fell on Mia, causing her death.
The Erikssons sued Nunnink for wrongful death and negligent infliction of emotional distress.
They alleged that Nunnink increased the risk of harm reasonably assumed by Mia when she allowed her to ride a horse that was unfit to ride because of prior falls and lack of practise and concealed this condition from the Erikssons.
Nunnink challenged the suit, arguing that the risk of death or serious injury to the horse rider is inherent in the sport of cross-country jumping and, alternatively, that Mia and Karan signed a pre-accident release, releasing Nunnink from any and all liability.
Based on these arguments, Nunnink contended that the facts showed that she neither owed nor breached any duty, legally causing the accident involving Mia.
The original trial court granted Nunnink's motion.
This week's appeal overturned that decision.
"As to primary assumption of the risk, ie, the element of duty, Nunnink failed to set forth facts in her separate statement of undisputed facts negating the Erikssons' allegation that Nunnink increased the risk of injury to Mia by allowing her to ride a horse that was unfit to ride because of prior falls and lack of practice," the appeals court ruled.
"Nunnink also failed to meet her burden of production as it relates to the element of breach of duty. As to express contractual assumption of the risk, Nunnink again failed to meet her burden of production that she was not grossly negligent," the appeals court said.
"We further conclude that, even if Nunnink met her initial burden, triable issues of fact exist as to duty, breach of duty, and gross negligence."
The Erikssons had demonstrated a triable issue of fact, the court ruled.
Mia began riding horses at age six and had trainers and coaches from that time on.
She began competing at age 13 or 14. By the time of her death at age 17, she had participated in 25-30 eventing competitions and other horse shows.
The judgment outlined Mia's competition history.
Mia trained for eventing at Tahoe Meadows, a 25-acre equestrian facility owned by the Erikssons. Nunnink was her coach.
Nunnink, the court noted, has been a professional trainer of horse riders for equestrian competitions for 25 years.
She gave Mia three horse-riding lessons each week, each lasting from one to three hours.
"At oral argument before the trial court, defense counsel clearly understood and articulated that the factual allegation relative to the fitness of the horse was the critical issue.
"We believe the error in his argument, however, is that he placed the burden on the Erikssons to establish duty rather than acknowledging that it was Nunnink's obligation to affirmatively negate the existence of a duty."
The court later noted: "Relative to the present motion, the record contains facts supportive of the allegation that Nunnink misrepresented certain facts to Karan as to the fitness of the horse."
The Erickssons lost an older daughter, Shana, 18, in 2003, when was was thrown from her horse at Cal State Fresno. Shana was on the equestrian team.
The couple sued the university unsuccessfully.