"We're going to nail James Earl Ray to the cross."

That, according to Rep. Mendel J. Davis (D-S.C.), is what one member of the House Assassinations Committee told him this week of the forthcoming public hearings into the 1968 murder of the Rev. Martin Luther King Jr. in Memphis.

Ray, King's convicted killer, is serving a 99-year term at Brushy Mountain state prison in Tennessee, but has been claiming innocence for years in an attempt to win a new trial.

The Assassinations Committee, which has been investigating Ray's family intensively, is apparently satisfied it has compiled a persuasive case against Ray.

But Davis, a member the House Administration subcommittee that supervises the spending for such inquiries, is skeptical, especially in light of accusations this week tht an undercover agent for the Assassinations panel had spied on Ray's brother, Jerry, purloined Jerry Ray's letters and secretly tape-recorded his conversations.

Members of the Assassinations Committee met privately yesterday afternoon to hear a report from chief counsel G. Robert Blakey on the dispute.

Rep. Christopher J. Dodd (D-Conn.), one member who attended, said later he was satisfied that "as far as the committee rules go, we did not violate those." But he said the question of whether a committee staff member, "on his own," may have engaged in questionable behavior needed further checking.

The self-described undercover agent, a former FBI informant named Oliver Patterson of Blackjack, Mo., said in a statement earlier this week that he had been recruited by a St. Louis-based investigator for the committee, Conrad (Pete) Baetz, and took his instructions from Baetz.

Blakey, who has been directing the staff investigation of itself, plans to issue a short, preliminary statement this afternoon. He intends to refuse to take any questions about it. Blakey then will hold a briefing on next week's hearings, reportedly as a "spokesman" for the committee whose name cannot be used.

Chairman Louis Stokes (D-Ohio) said the investigation of Patterson's allegations would be completed "as soon as possible," but did not know how quickly it could be done. In any event, Dodd said. "We're not going to be derailed over this issue."

The accusations were orchestrated by Mark Lane, now James Earl Ray's lawyer, who had enlisted Patterson as a committee defector. James Earl Ray is scheduled to testify before the committee on Wednesday, reportedly to accuse it of conspiring to deny hime a fair trial.

The controversy prompted the House Administration subcommittee, of which Davis is a member, to with-hold additional funding for the investigations. At a closed-door caucus called yesterday afternoon by House Administration Chairman Frank Thompson Jr. (D-N.J.) to reconsider the decision, the subcommittee's Democrats reaffirmed their intention to hold off until next month on the Assassination panel's request for an additional $790,000.

Subcommittee Chairman John H. Dent (D-Pa.) and Thompson told a reporter later that they have also ordered their staff to examine the Assassinations Committee's financial records and put them in order. Dent said the committee has not been properly reporting its spending, especially in the area of its 56 secret consulting contracts.

At the same time yesterday afternoon, the Assassinations subcommittee investigating President Kennedy's murder in 1963 took testimony in executive session from former Central Intelligence Agency director Richard Helms.

Deputy director of the CIA's covert operations section at the time of the assassination, Helms told reporters during a break that no one would ever known who or what Lee Harvey Oswald, named by the Warren Commission as Kennedy's assassin, represented.

Asked whether the CIA knew of any ties Oswald had with either the Soviet KGB or the CIA, Helms paused, and said with a laugh, "I don't remember."

Pressed on the point later, he told a reporter, "Your questions are almost as dumb as the committee's."