Daniel Minchew, the chief accuser against Sen. Herman E. Talmadge (D-Ga.), apparently lied on three separate polygraph examinations he was given in January by the FBI, federal experts testified yesterday.

Members of the Senate Select Committee on Ethics heard a cross fire of conflicting assessments about Minchew's credibility from three polygraph experts during a hearing on allegations of financial wrongdoing by Talmadge.

Minchew, who was Talmadge's chief aide until 1974, has claimed that Talmadge was aware of a secret bank account at the Riggs National Bank here that contained illegal Senate reimbursements and mostly unreported campaign contributions. Talmadge has denied the allegation and accused Minchew of being an embezzler and a liar.

An FBI assessment of Minchew's polygraph reactions said the former Talmadge aide was "clearly deceptive" when he answered during a test that Talmadge knew about the secret Riggs account.

James K. Murphy, the FBI polygraph expert who administered the three tests between Jan. 11 and Jan. 22 to Minchew, told the ethics panel that Minchew also appeared to lie when he said that Talmadge knew campaign funds were funneled through the secret account. Murphy's boss, Paul Minor, who is the FBI's "polygraph program coordinator," seconded Murphy's interpretation of the results.

But a private polygraph specialist hired by Minchew's attorneys, Benjimin F. Malinowski, said that he found "no reaction indicative of deception" in Minchew's answers to similar questions during a polygraph test he administered in December.

A fourth polygraph expert, Raymond Weir, testified Monday that he, too, tested Minchew last month and found that he told the truth when he said he gave Talmadge cash from the secret account. Weir did not ask whether Talmadge knew of the account itself.

"This is not the best day the polygraph has ever had," said a committee member, Sen. Jesse Helms (R-N.C.), as the ethics panel sought to make sense out of the experts' conflicting testimony.

Meanwhile, a spokesman for Talmadge denied yesterday that the senator knew in 1977 that his office got over $25,000 in improper Senate reimbursements between 1973 and 1976.

Talmadge has sworn under oath to the Senate Ethics Committee that he did not learn of the overreimbursements until last June. He repeated his claim in a dramatic opening statement to the hearing last week.

But atlanta attorney W. Stell Huie, who represented Talmadge's former wife, Betty, in their bitter divorce action in 1977, confirmed a report in The Washington Star that the question of the reimbursements had been raised by him in an August 1977 deposition of Talmadge.

"I brought it up during a deposition I took from him in 1977," Huie said in a telephone interview yesterday. He said the overdrafts from the Senate were spotted by accountants he hired for the divorce proceeding.

Huie said he also brought the overdrafts up in another deposition he took in September of 1977 when he questioned Lawrence W. Earls, Talmadge's accountant. He said that the matter was not pursued further because it was not relevant to the divorce.

Gordon Roberts, Talmadge's press spokesman, said yesterday that while he had not seen the Huie depositions, he had been at two meetings of the senator and his staff last June when the overdrafts were discussed for the first time. "There is no question in my mind that he did not know of them before then," Robert said. CAPTION: Graph, Readings in polygraph examination of Daniel Minchew, Talmadge's chief accuser. Photos by James K. W. Atherton - The Washington Post; Picture 1, James K. Murphy, FBI polygraph expert, at Senate ethics panel hearing.; Picture 2, Sen. Herman E. Talmadge awaits hearing at which FBI experts testified that his chief accuser apparently lied on polygraph exams. By James K. W. Atherton - The Washington Post