What does the aviation accident lawyer need to prove in order to win a "design defect" lawsuit against the manufacturer of the aircraft that injured his client?   

It varies from state to state. But it’s never enough simply to prove that the aircraft‘s design caused the accident or injury.  The victim’s lawyer always has to prove more than that.  One way for the aviation lawyer to win the lawsuit under California law is to prove to the jury all of the following things:

  1. That the pilot did not misuse the aircraft, but instead operated it in a way the manufacturer could have anticipated;Zodiac CH 650
  2. That the aircraft’s design presented a real risk of injury, and not just a remote possibility of injury; 
  3. That a different, safer design would have avoided the accident or injury, and
  4. That the safer design was “feasible.”  In other words, a safer design would not have been too expensive, been too difficult, made the aircraft too heavy, significantly detracted from the aircraft’s performance or usefulness, or presented other serious drawbacks.

To support the case, the victim’s lawyer can present to the jury evidence such as the testimony of expert engineers, pilots or eyewitnesses; documents from the manufacturer’s files; pieces of the aircraft wreckage; “mock-ups” of safer, alternative designs; and laboratory test results.  He cannot, however, use any of the conclusions or opinions contained in the National Transportation Safety Board report concerning the accident.  That’s because the NTSB’s opinions are inadmissible in court.

After all the evidence has been presented, the judge explains to the jury exactly what the victim’s lawyer needed to prove in order to win. The explanation is called the "jury instructions."  The judge gets the instructions from standard, pre-published forms that he modifies as needed for the particular case. 

For the victim to win, the jury must agree, after reviewing all the evidence, that his lawyer proved his case by a "preponderance of the evidence."  That means that the evidence, taken together, showed that each element of the victim’s case was “more likely than not” true.  The lawyer need not prove his case “beyond a reasonable doubt.” That standard of proof applies only in criminal cases.