Yamaki testified that he sought Carona's recommendations for state boards and commissions appointments.
"He was the sitting sheriff, the elected sheriff of one of the most populous counties in California," Yamaki said. "I valued that opinion."
Carona is facing charges he sold access to his office for cash and gifts.
His wife and former mistress also face charges, but are being tried separately.
Yamaki said Carona might recommend someone but that would not necessarily mean they would be appointed.
However, if Carona's word was negative, Yamaki said, "I probably would pass on that person" and not make the recommendation to Davis.
Yamaki said there are more than 50 fair boards in the state, each with nine people, so he often faced a deadline in filling positions.
Assistant U.S. Attorney Brett Sagel asked on cross-examination whether Yamaki relied on Carona's truthfulness about his recommendations.
Sagel questioned Yamaki as to Carona's own appointment, along with Hoffman, to a state commission, asking if he would do so knowing that the two had a relationship.
"I can't speak for the governor but I would want to know," Yamaki said.
Sagel pointed out that both Carona and Hoffman wrote "no" when asked on application forms if they had anything in their backgrounds that might cause embarrassment.
When asked if Hoffman would not have been appointed had he known about the relationship Yamaki said he could not speculate.
"Certainly I would make sure that she wasn't on the same commission as his wife," Yamaki said.
City News Service contributed to this story.
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