When you take your employer to court in New York for a Jones Act negligence claim, you must show that he or she did not act in the way a reasonable person would. The Manual of Model Civil Jury Instructions for the District Courts of the Ninth Circuit explains that the negligence could be a failure to make sure the vessel is seaworthy, or it could be failure to hire an adequate number of crew members who are trained for their duties, among other violations.
You have the burden of proof in court to demonstrate to the judge and jury that the shipowner's negligence caused the accident that injured you. However, it may be that you were somewhat negligent yourself when the accident happened. For example, you might have been careless in performing your duties when an issue occurred with equipment. Maybe the accident would not have been as severe if you had been paying attention, or wearing proper personal protective equipment. This does not mean your negligence case will fail.
If the shipowner is able to provide proof that you were partially responsible, and the jury agrees, they would attribute a percentage of the fault to you. However, this would not change the amount they award you. The judge would take your percentage of the negligence out of the final award.
There is an exception. If your injury occurred because the shipowner violated one of the Coast Guard's regulations, contributory negligence does not apply, and your award would not be affected. Other factors may be relevant in your case, so this information should not be taken as legal advice. However, it may give you an idea of what to expect when you make your Jones Act claim.