More: The park service engineer alerted the administration to the peeling issue in an email sent June 11, which the U.S. attorney's office included in a court filing Wednesday. Prosecutors said that they were "not aware of or in possession of" documentation that the Interior Department had of installation problems at the time they charged Hearn.

The engineer noted that the "top layer of liner has peeled," adding that it is "very thin and will not impact the strength of the liner." The person explained in the email that the "contractor stated that the peeled area was overspray' from spraying the perimeter joint with polyurea," according to the Justice Department. The engineer warned that the issue could "lead to a 1'-2' strip that is vulnerable to peeling."

The engineer sent the message to Interior Department and park service personnel.

"These statements cast significant doubt that the defendant caused damage to the lining," Assistant U.S. Attorney Michael Spence said in the filing Wednesday, referring to the engineer's warning and Hearn. "This information " that the piece of liner peeled by the defendant was overspray, of little or no value " was first furnished to the prosecutors weeks after the grand jury indicted the defendant."

Spence argued that these "late provided documents showing blistering and peeling, as noted by the contractors, would sabotage the government's ability to meet its burden of proof" in the Hearn case.