It's the kind of evidence any plaintiff in an accident case dreams of: the equivalent of a confession by the company under attack that its product or procedure was faulty. But traditional courtroom rules ban showing that evidence to a jury.

That tradition is now changing. A lot of jurisdictions are refusing to buy the change, but every one that does is removing from companies important protections in liability suits.

The evidence is that at some point after the accident, the defendant company altered the design or practice to make things safer. To a jury trying to decide whether a company should pay damages to an accident victim, evidence of such an after-the-fact fix-up "makes the most common sense," argues Columbus, Ohio, lawyer Jason A. Blue. "A repair or a change becomes an admission."

Blue, who chairs the Product Liability Exchange Committee of the Association of Trial Lawyers of America, is litigating one such situation now. It's a suit against an automobile manufacturer by a victim who traces his injuries to the fact that the collapsable steering wheel in his car did not collapse at the time of impact. It was held rigid by a bracket that was removed in later models, Blue claims, but the jury that will hear the case cannot be told about the redesign. Similarly, the U.S. Court of Appeals in Cincinnati ruled last summer that a jury hearing a suit by a seaman injured on a slippery deck during a storm cannot be told that after the accident the shipowner stopped hosing down the decks in such weather.

The ban on such evidence is based on one of the Rules of Evidence that govern federal courts. It says, in typical legalese, "When, after an event, measures are taken which, if taken previously, would have made the event less likely to occur, evidence of the subsequent measures is not admissible to prove negligence or culpable conduct." But there is a lot of debate in law journals about just how applicable that rule should be to cases like these involving the auto steering wheel column or the slippery decks because in those cases strict liability applies. That means that the plaintiff does not have to prove negligence.

As long ago as 1974, California decided that in strict liability cases there's no reason not to let the jury know when a defect has been corrected later. Court decisions laid down the same rule in Nevada, Wisconsin and South Dakota, and it is embedded in procedural rules in Hawaii, Alaska, Colorado, and Wyoming. Maine allows evidence of later design changes in any sort of liability suit. And the federal appellate court covering district court trials in Minnesota, Arkansas, Missouri, Iowa, Nebraska, Minnesota and the Dakotas has time and time again come to the same conclusion.

But other states--including such important industrial centers as Michigan, Ohio, and New Jersey--and most of the federal courts of appeals that have looked at the question continue to exclude the evidence. Their reasoning: soceity benefits when a product is improved, but if the courts are going to look at design changes as proof that the earlier approach was hazardous, it is going to stifle the kind of improvement that should be encouraged.

"I'm not totally convinced about that incentive argument," says Georgetown University law professor Joseph A. Page, an authority on product liability litigation. "There are other very powerful reasons for making post-accident changes. Just think about Tylenol." Basically, he says, the risks of not making an item safer once accidents have shown a previously unrecognized danger far outweigh the dangers of losing a few law suits. Continuing to market a faulty product will not only court more suits, but will open the company to the threat of having to pay punitive damages as well, if they have not heeded the warning of the early accidents.

That's pretty much what the California judges said in 1974 when they decided to admit such evidence. They called it "manifestly unrealistic" to suggest that a company "will forego making improvements in its product, and risk innumerable additional lawsuits and the attendant adverse effect upon its public image, simply because evidence of the adoption may be admitted in an action founded on strict liability."

Actually, that way of looking at things seems to be influencing judges even in the courts that cling to the old rule. "I think that design changes will become limitedly admissible, depending on the fact pattern," Blue predicts. For instance, he says that judges will let testimony about later repairs go to a jury when the lawyer's aim is not to show that the company knew that the item was unsafe, but to show that it was in fact responsible for its operation. Other exceptions are being made when the purpose of the evidence is to show that a better technology was available, or that a witness for the company may not have told the whole truth.

That was the courtroom strategy involved in a case decided two months ago by a Florida District Court of Appeals. The case was brought by a plaintiff who suffered an eye injury when a bottle of Almaden champagne popped its cork. An official of the vineyard testified that a natural cork would pop on its own only if the bottle had been mishandled. The appellate judges said that the plaintiff should have been allowed, in order to counter that testimony, to tell the jury that after the accident Almaden began putting a warning label on all its champagnes telling consumers to take care because "the stopper will eject soon after the wire hood removal."