Medgar Evers, one of the most significant and good activists of the civil rights campaigns of the 1960s, was murdered in 1963. Suspicion fell promptly on Byron De La Beckwith. Within a year he was brought to trial, charged with the murder.

The jury did not convict. A second run through the American criminal justice system occurred a bit later, and again Beckwith emerged free.

Now, 27 years later there is said to be "new evidence" and a third run through the justice system is contemplated in Mississippi. The state of Tennessee is asked to extradite Beckwith, now an old man in poor health, to Mississippi.

Suppose Beckwith is innocent. No jury, after all, has found him guilty in the two attempts to convict.

How many of those who might testify are alive or competent now? The decades can do wonderful things to one's memory. I recall an oral history project of Memphis State University after the murder of Martin Luther King in Memphis. Volunteer teams with tape recorders interviewed, within very few days of the crime, an almost endless number of people associated with King, with the garbage workers (whose strike caused King to be in the city) and many public officials and police officers.

They spoke while the crime and the shock were fresh, long before opinion solidified and well before details of the crime were known.

What those people said then is not what they would say now, in many cases; now that the full dimension of the crime has been seen.

An old saw reminds us that justice delayed is justice denied. It works in all sorts of inconvenient ways.

If Beckwith had never been charged and if it were now discovered he might well have been the murderer, a case could be made for bringing him to trial even now. But almost immediately he was the main suspect and his trials were prompt. And he was not found guilty.

If at first you don't succeed, try try again is a pretty saying, but it never was and never should be the controlling rule of American criminal law. The system exists to settle disputes, and with luck to settle them justly and without violence to agreed-on constitutional principles. But in any case, to settle them once and for all.

Take the case of Marion Barry. It was widely said by responsible opinion makers that "nobody wants the mayor to go to jail," and of course that was not so. A great many people prayed fervently he would go to jail, since boiling in oil seemed beyond reach.

But despite the greatest efforts of the prosecutors the mayor was not found guilty of a felony, and the jail sentence of six months (for a misdemeanor) is under appeal.

Should those who think the mayor's damage to the city deserved far heavier sentencing simply wait a few years, then try to reopen the case, possibly under new charges? Why not wait till the mayor is old and sick and many witnesses are dead, or have had years to revise their memory?

Suppose Beckwith did murder Evers. Suppose the Mississippi juries simply refused to convict him even though they had no doubt he was guilty.

It is often argued that a weakness of our system of law is simply that citizens chosen at random, who need not even know how to read and write, have the authority to pronounce on the facts. No matter what the facts are, a jury may in practice simply refuse to believe them, no matter how "unarguable" those facts are. Thus an innocent man may be found guilty and a guilty man may go unconvicted.

But that is the legal system we have. It is the system officials swear to uphold, and it is the system we have the duty either to abide by or else to change.

I don't think we will find one any better. I don't think it should be used to run a man time after time, through the decades, through trials brought in the hope that at last he may be convicted. Guilty or innocent, two trials are enough. Enough for Barry and enough for Beckwith.

Tennessee should refuse extradition to Mississippi. If juries failed in achieving justice twice, then that is the responsibility of Mississippi. Tennessee should not be party to the charade of "new evidence" 27 years later. American justice should not be subjected to this kind of strain, by which a man who may be innocent is repeatedly charged with a crime for which two full-dress legal proceedings failed to convict him.