MADISON, Wis. — Target Corp. destroyed evidence crucial to a Wisconsin customer's claim that her family was sickened by chemicals that were packed in a box that she thought contained an air mattress, a state appeals court ruled Thursday.

The ruling stems from a lawsuit Cheryl Cody and her family filed against the Minneapolis-based retail giant in 2009. The Sauk City woman alleges that she bought what she believed was an air mattress from a Madison store in December 2006, but when she opened the box, she found a jar of ant and roach killer with a tube coming out of the top of it.

She took the box back to the store, where workers placed it in the loss prevention manager's office. The next day Cody called a Target customer service employee and complained about the items in the box and said her family was having allergic reactions.

The store's loss prevention manager later took the box and its contents to Target's chargebacks department, which processes items that can't be placed on store shelves. The corporation subsequently destroyed the items, according to filings in the case.

Dane County Circuit Judge William C. Foust ruled the destruction of the box and its contents amounted to spoliation, a legal term that equates to the intentional destruction or concealment of evidence. As a sanction, Foust ruled the family doesn't have to prove the box's contents caused their illness.

Target appealed, contending Cody's call wasn't enough to signal a lawsuit may be on the way and evidence should have been preserved. The retail chain also contended the box's destruction wasn't egregious enough to warrant a sanction that so dramatically reduces the family's burden of proof.

The 4th District Court of Appeals agreed with Foust's conclusion that Cody provided the store with substantial information beyond the notice of an injury. The court pointed to notes the customer service worker took during Cody's call that indicate Cody identified the "peculiar" contents of the box, that it contained poison, members of her family were sick and she was very upset.

"We cannot say that the circuit court's finding that Target's destruction of the evidence constituted spoliation was clearly erroneous," Judge Gary E. Sherman wrote in the court's unanimous opinion.

The appellate court also found Foust's sanction was proper since Target's actions made it impossible for Cody and her family to prove the contents of the box caused their illness.

The court sent the case back to the circuit level for further proceedings.

Target's attorney, listed in court documents as Jeffrey Nichols, didn't immediately return a telephone message.

Cody's attorney, Patrick Miller, said the woman's family is still suffering from circulation problems, rashes and orthopedic issues. He said the appellate ruling saved their case. With the contents of the box destroyed, he had no way of proving they caused the family's problems. Now he doesn't have to deal with that issue.

"It made what was previously a case that was impossible to prove. It's gone to the other end of the scale. I don't have to prove cause (of the illnesses). If we didn't win this appeal, we're essentially at a point where the case would have been dismissed," he said. "It's everything we wanted."