With sirens wailing and red lights flashing in the background, the ambitious but little-known lawyer stood in a downtown alley and talked tough about law and order.

"The city is a jungle," said William A. Swisher, as he promised in a slick television campaign commercial to keep the streets safe from criminals. The commercial, quickly branded a blatant appeal to racism in a campaign against the city's lone black officeholder, helped catapault Swisher in 1974 to the job he sought as the city's chief prosecutor.

Today, prosecutor Swisher went on trial as a criminal defendant himself -- charged with selling the powers of his office to James H. (Jack) Pollack, the political boss who, prosecutors said, put him in office.

"Simply put, Jack Pollack . . . bought himself a state's attorney," Assistant U.S. Attorney Daniel Hurson told jurors today, as Swisher's trial opened in federal district court here.

Pollack, the legendary boss, died more than two years ago, but to hear Hurson talk to jurors today, it seemed Pollack should have been sitting in the courtroom as Swisher's codefendant. Indeed, the word around the courthouse where Swisher's cronies congregate is that the government's case is really against a dead man -- Jack Pollack.

"When they can't get the powerful people," lamented a retired Baltimore judge who is heading Swisher's defense fund, "they get the little potato."

As well as a "little potato."

As well as a "little potato," Swisher is known around town as a nice guy, an affable guy, rather bland as a lawyer, and according to one observer, "a sort of a nebbish." The prosecutor is well aware of his less than flattering image, particularly as portrayed in the Baltimore newspapers. "If you judge me by the press," he told a reporter recently, "you'd think I was a sinister, dim-witted hack who couldn't find his way across the street."

Today, Bill Swisher, the most poserful law enforcement official in city government, sat in court as Hurson charged that he halted a major public corruption investigation after the men under suspicion paid off his mentor, Pollack.

State's Attorney Swisher, head of the largest prosecutor's office in Maryland, also handed over to Pollack the power to hire his staff lawyers, and job applicants sometimes were required to make "outright cash payments" to Pollack before they were hired, Hurson charged.

"Keep in mind, this was a partnership," Hurson told the jury."Mr. Pollack is dead . . ., but Mr. Swisher is very much alive, and he is still the state's attorney."

When the defense got its turn to talk to the jurors, lawyer Aubrey M. Danniel Iii said the evidence would show the relationship between his client and Pollack was not a corrupt one.

What the government called an illegal surrender of Swisher's hiring power to Pollack, Daniel described as simple political patronage, a routine practice of presidents, governors and other politicians.

The corruption investigation that Swisher allegedly halted actually was terminated by Swisher's predecessor before Swisher ever took office, the defense counsel said.

The events that led Swisher from the richly paneled office of the Baltimore state's attorney to that courtroom six blocks away began just before July 1, 1974. On that day Swisher officially filed to run in the Democratic primary for state's attorney, hoping to capture the office that controls criminal prosecutions of everything from parking violations to murder in the city of Baltimore.

Many say, and the prosecutors will attempt to prove, that Swisher was plucked from the obscurity of a neighborhood law practive and neatly packaged as a candidate by Pollack and George Hofferbert, the political chieftain from Swisher's own German-Polish neighborhood in East Baltimore.

The 46-year-old Swisher, still stung by the repeated accusation that he was Pollack's and Hofferbert's Pygmalion five years ago, insisted recently: "Of course, I made the decision [to run] myself."

Before that decision, Swisher, a pudgy man with graying hair and a courtly manner, was hardly known outside the political clubhouse of his native East Baltimore and the office where he had built his law practice. But by taking on Allen, the city's only black to hold a citywide elective position, Swisher soon was thrust before the public -- called a racist by the black community and a law-and-order hardliner by whites frightened by a rising crime rate.

The image was due almost entirely to that TV commercial slapped together in the waning days of the primary campaign after Swisher paid a visit to political advertising wizard Robert Goodman.

To film the "city if a jungle" spot, Goodman recalls, he put Swisher in front of a lights-flashing, siren-wailing ambulance in an alley at dusk, told him to pull down his tie a bit "to give him a little macho," and created a "30-second piece Swisher ran the kazoo out of."

Goodman said he never considered it racist.

Swisher reenforced the image created in that commercial last winter when predominantly black bands of looters ravaged several Baltimore neighborhoods after the February blizzard. On a television news show, Swisher said he would not prosecute businessmen who chose to shoot "these animals and criminals" who "come out of the corners" when police are immobilized.

But the go-get-'em prosecutor is not the man his friends and colleagues know.

"There's a real naivete about this guy," says one local lawyer, who has represented criminal defendants prosecuted by Swisher's office. "He's kind of bewildered by all this indictment and trial business."

One day, the lawyer recalls, he spotted Swisher walking down a street near the courthouse with a dirty, dog-eared copy of the 27-count indictment against him tucked under his arm.

Retired Judge Avrum Rifman, remembers Swisher as a quiet, unassuming defense attorney in the years before his election. A man who put himself through the University of Baltimore Law School by working as an insurance claims adjuster. Swisher is considered a competent lawyer by many colleagues but certainly not a star. He no longer ventures into the courtroom, preferring to supervise the 90 or so attorneys on his staff.

Away from his office, Swisher is a devotee of the crab feasts, bull roasts and banquets that are the meat and potatoes of political life in Baltimore. He often is seen at more than one a night.

In restaurants, one friend says, he is a "notorious noncheck grabber."

One night at Sabatino's, a popular political haunt in Little Italy, Swisher joined several lawyers and a city judge. The friend recalls Swisher didn't order, but ate the judge's unfinished steak dinner. When the check came, Swisher refused to chip in, arguing that he had not ordered a thing, the friend recalled.

"People were laughing, and of course, he finally good-naturedly paid his share," said the friend, who added that Swisher seems to relish polishing his image of frugality.

The image of an affable, frugal nebbish is in sharp contrast with that of the legendary Jack Pollack, whose spectre Swisher cannot escape even two years after Pollack's death.

The 6-foot, 2-inch prizefighter-turned-powerbroker was Baltimore's most powerful boss in the 1940s and 1950s. He picked judges, city council members and legislators, got them elected and often controlled their votes in Baltimore and Annapolis.

Swisher, nattily dressed and smiling, lounged recently behind his desk at his criminal courthouse office his walls adorned with some of the Baltimore newspapers' most unflattering cartoons of him. One, from the 1974 campaign, has him standing in from of demonic apparitions of Hofferbert and Pollack.

Seemingly almost to relish his long-running feud with the press, he showed off the cartoons to a visitor.

It was the press, say says, that branded him a racist just because he was running against Allen, a black and the newspapers' choice for the office.

He scoffed at the idea that any of his remarks have been racist: "Is the word 'jungle' racist? Of course not."

Talk of the indictment was off limits in the interview, except that Swisher insisted it had not disrupted the state's attorney's office in any way.

But that's not the story the troops tell.

"The whole office is under a cloud," one exasperated state's attorney blurted out. "You've got a prosecutor being prosecuted."