Poorly designed and built levees in the New Orleans area caused 92% of the flooding that hit a nursing home where 35 residents drowned after Hurricane Katrina, according to a defense witness. He was testifying Tuesday in the case of two facility owners on trial for negligent homicide.

St. Rita’s nursing home would have taken in less than a foot of water if the levees had held, said Ivor Van Heerden, deputy director of the Louisiana State University Hurricane Center. Instead, a much larger wall of water overtook the facility owned by Sal and Mabel Mangano and dozens died.

The testimony contradicted a prosecution expert, a retired meteorologist with the National Hurricane Center, who had testified earlier that levee problems had led to only about a foot of the seven feet of water that filled the nursing home.

The prosecution, meanwhile, earned a dramatic victory Tuesday, successfully challenging whether a document from the Louisiana Nursing Home Association could be used as defense evidence. The document showed that 32 of 74 nursing homes in the New Orleans area sheltered in place and did not evacuate, just as the Manganos did.

After losing motions before the trial judge and then the 1st Circuit Court of Appeal late Friday to block the list’s introduction, prosecutors appealed to the Supreme Court on Tuesday morning. The state’s highest court ruled 4-3 against allowing the document into evidence.