They could have, but they are not required to. There is a presumption that the witness will be hostile. If you read the trial transcripts from the 2001 Shawangunk Conservancy trial you will see that Mr. Van Valkenburgh was extremely uncooperative on cross examination. He would not admit the sky was blue. It was sufficient that they already had the previous trial testimony, which contradicted what Mohonk was arguing in this case.