The tactic was called "mudslinging" by attorney Isaac Hall, who represents three environmental groups seeking an environmental assessment of Superferry operations.

Kaufman's testimony about humpback whales, particularly their risk of being harmed by the fast-moving ferry, is one of the issues confronting Circuit Judge Joseph Cardoza as he weighs whether to allow the Superferry to resume interisland service until a court-ordered environmental assessment is completed.

Lamon's attack on Kaufman "has nothing to do with whether Hawaii Superferry should be operating," Hall said.

Hall represents Maui Tomorrow, the Sierra Club and the Kahului Harbor Coalition. They won an Aug. 23 Hawai'i Supreme Court ruling that the state erred in exempting $40 million in ferry-related harbor improvements from an environmental review.

Qualified as an expert witness on whales in the ongoing evidentiary hearing, Kaufman has testified about the potential danger the Superferry's 350-foot double-hulled catamaran, Alaka'i, poses to dolphins and endangered humpback whales, which migrate to Hawaiian waters from mid-October through early July.

Late Monday, Kaufman maintained the ferry could kill or seriously injure whales that cross its path.

He based his opinion on research of whale strikes and the probability of fatalities when considering a boat's size, speed and weight.

In attempting to discredit Kaufman, Lamon cited a March 2000 announcement of a settlement between the Pacific Whale Foundation and the National Oceanic and Atmospheric Administration.

According to Lamon's representations in court, the settlement involved a Pacific Whale Foundation agent who may have either failed to allow inspection of the foundation's records or falsified data on research activities to the National Marine Fisheries Service. The agent was not identified.

Lamon told Cardoza he wanted to cross-examine Kaufman about the settlement to show he was not a credible witness and to question his foundation's research practices.

"I think this is proper impeachment," Lamon said.

But Cardoza would not allow Lamon to use the NOAA settlement, saying there was no proof that Kaufman was directly involved in the nearly 10-year-old matter.

Cardoza said it was "not your traditional attack" against the credibility of a witness and could not be used since it was unclear what misconduct, if any, the foundation agent was involved in.

The judge also noted Kaufman's testimony last week was not connected to any of the research activities cited in the NOAA settlement.

Other attempts by Lamon to question Kaufman's credibility were similarly unsuccessful. One involved the rejection of a foundation research permit in 2001. Another stemmed from alleged harassment of whales by the foundation, an allegation denied by Kaufman.

The Maui environmental groups say an environmental review is needed to address concerns about the introduction of invasive species, possible collisions with whales and more traffic congestion on Maui.

The evidentiary hearing entered its fourth week Monday. It's been more than a month since the Superferry suspended its interisland service after only two days in operation in late August.

Kaufman is expected to return to the witness stand when the hearing resumes at 10 a.m. today.