As the jury remained deadlocked after its 40th hour of deliberation, defense attorneys for the "Chicago 7" yesterday filed a motion to end the deliberation and call the five-month procedure a mistrial.

The jury is hung, defense lawyers speculated for the first time yesterday. "It's obvious that the jury is not able to reach a decision after four days of deliberations," Leonard I. Weinglass, one of the two defense attorneys, said.

But despite a plea for immediate action, the defense does not expect Judge Julius J. Hoffman to acquiesce easily to the mistrial motion.

Hoffman prides himself on the fact that he has had 23 guilty verdicts out of 24 in his courtroom recently. On the 24th case, the jury was deadlocked and Hoffman jailed one of the jurors for contempt. (He allegedly read a news clipping on the trial.)

If the 10 women and 2 men return to the courtroom today and report a deadlock. Hoffman can still deny the defense motion and send the jury back to try again.

In doing so, Hoffman will deliver the so-called "Allen charge," known also as the "shotgun charge." instructing the jurors in the minority to reconsider the majority view and vote according to their conscience.

The Chicago Court of Appeals had indicated that it considers the Allen charge an attempt to browbeat the jury. A study of its use has shown that juries return with a guilty verdict almost 90 per cent of the time when the judge sends the jury back.

It is generally agreed that the longer the jury deliberates, the better the chances for the defendants. However, defense attorney William Kunstler said a very long delay can mean the jurors are "bargaining away the rights of some defendants to reach agreement on the others."

The seven defendants are each charged twice-with conspiracy to cross state lines to incite to riot and one count apiece of "substantive acts" relating to the conspiracy.

Earlier yesterday, Kunstler said "it would be a miracle" if all the defendants were acquitted. but that he expects some "compromises."

"Some of the defendants will be convicted. others will be acquitted or the jury will hang deadlocked on all of them," Kunstler said.

A study of other juries sequestered during long trials shows that they rule in favor of the prosecution 66 per cent of the time.

Should the jury-even after Hoffman sends them back to deliberate under the Allen charge-fail to reach a verdict. the government will probably drop thecase rather than begin another trial.

The Justice Department admits the case has cost $250,000 to prosecute. Unofficial estimates run much higher.

More important, however, the trial has tied up the number one United States District Attorney in the most overloaded federal district in the country and received extremely critical press throughout the country.

The government has nothing to gain from retrying the case-either in the courtroom or the press.

As Tom Hayden, one of the defendants, said early in October, "Old Julius is not stupid. He is shrewd and he knows he's got us either way. If we object to this trial, he can jail us for contempt for three years and appealing the verdict won't help at all."