Noted British penal expert Sean McConville certainly got the mayor's number in his draft report on D.C. corrections. The exhaustive study of the city's jail and prisons repeatedly refers to Mayor Marion Barry's facile, and sometimes evasive, style of politicking on this critically sensitive matter.

The report, which became public last week, will be an affront to Barry fans who credit him with engaging in a tactically brilliant campaign to stave off judges, prosecutors, inmates and Congress, all of whom want different things rather badly from him. The mayor has managed to keep them all at bay without laying a brick of the new prison he says he favors.

McConville, however, is not so impressed with the mayor's handling of prison conditions and expansion of the system.

The University of Illinois criminology professor accuses Barry variously of "passing the responsibility"; "flapping his arms"; adopting "various changing postures," and using a "time-honored political device of diverting policy criticism and repercussion in what was certain to be a controversial decision."

The controversial decision, the one that has not yet been made, is of course, where to build a new prison.

Ever since early 1985, after a little arm-twisting, Barry has been saying he favors constructing a new prison to relieve crowding in the jail, so long as it is placed on federal land and financed by the federal government.

His reluctance to pick a site for the new prison is documented in the McConville study.

It is typical that even as the contents of the draft report were being reported by Post staff writer John Ward Anderson, the mayor was adding a new wrinkle to his posturing on prison construction.

Emerging from a meeting with Justice Department officials last week, Barry said he would undertake to design and build a new prison as soon as he received a list of possible prison sites designated by the federal government. From that list, a site for a new prison would be chosen, he said.

An innocuous sounding declaration, the mayor's statement distinctly moved the onus of site selection closer to federal officials and away from him.

Barry's comment, delivered after federal officials rescinded an agreement to transfer District prisoners to the federal prison system, appears to lay the groundwork for future onus-shifting by the mayor. Perhaps it will later be said that the Justice Department, in fact, foisted a site on a reluctant mayor and his city.

The significance of Barry receiving a list of prospective sites, rather than drafting one himself, can be better appreciated with some background.

As early as January 1985, City Administrator Thomas Downs disclosed that he had prepared a list of prison sites.

Later in the year, after a prison study commission declared it was opposed to building a prison, the mayor's aides again examined sites, Barry disclosed in a press conference last week.

In addition to these separate site examination exercises, the city produced a study of sites for a prison back in 1975 when Northern Virginia officials were pressing for the removal of D.C. correctional facilities at Lorton.

That makes a total of at least three efforts that have been made to identify sites for the now mythic prison. And yet, Barry says he still needs a list of possible sites from federal officials.

What the mayor appears to be looking for is not a site, but someone to blame it on. The strategy of shifting responsibility elsewhere no doubt is attractive because, in truth, it has worked exceedingly well so far. Why quit now?

McConville notes the numerous occasions when the mayor has tried to deposit responsibility on somebody else's doorstep.

Last summer when U.S. District Judge William B. Bryant ordered a population limit at the city jail, the mayor blamed Bryant, saying, "If we have to let . . . criminals on the street, that is the judge's responsibility." Next, asserting that technically, the U.S. attorney general has custody of D.C. prisoners, the mayor cleverly nudged the Federal Bureau of Prisons to accept surplus District convicts.

When federal officials halted the arrangement because they thought the District of Columbia wasn't doing its share to reduce crowding at the jail, the mayor again invoked the attorney general and said he hoped the federal bureau would take more inmates.

In addition, the City Council and mayor last summer appointed a prison study commission -- months after the mayor had committed himself to the Congress to build a new prison.

The commission was chartered to decide whether and where to build a prison. The result was, in effect, a six-month stall by Barry and a report from the commission recommending that no prison be built.

McConville pooh-poohed the commission as a time-honored vehicle for diverting political criticism, then pointed out that the "decision as to location . . . was essentially political rather than a matter for a nonelected commission."

Finally, the criminologist concluded that the best way out of the corrections department's chronic problems would be the appointment of an outside manager to take it over -- a "bitter fruit" for the city, as he put it.

Indeed, it would be a bitter fruit if, in shunting aside responsibility for corrections, the Barry administration found itself with none.