On 22nd July, 1916, employers in San Francisco organized a march through the streets in favour of an improvement in national defence. Critics of the march such as William Jennings Bryan, claimed that the Preparedness March was being organized by financiers and factory owners who would benefit from increased spending on munitions.
During the march a bomb went off in Steuart Street killing six people (four more died later). Two witnesses described two dark-skinned men, probably Mexicans, carrying a heavy suitcase near to where the bomb exploded. The Chamber of Commerce immediately offered a reward of $5,000 for information leading to the arrest and conviction of the dynamiters. Other organizations and individuals added to this sum and the reward soon reached $17,000. Offering such a large reward was condemned by the editor of the New York Times claiming it was a "sweepstake for perjurers".
On the evening of the bombing Martin Swanson went to see the District Attorney, Charles Fickert. Swanson told Fickert that despite the claims that it was the work of Mexicans, he was convinced that Tom Mooney and Warren Billings were responsible for the explosion. The next day Swanson resigned from the Public Utilities Protective Bureau and began working for the District Attorney's office. On 26th July 1916, Fickert ordered the arrest of Mooney, his wife Rena Mooney, Warren Billings, Israel Weinberg and Edward Nolan. Mooney and his wife were on vacation at Montesano at the time. When Mooney read in the San Francisco Examiner that he was wanted by the police he immediately returned to San Francisco and gave himself up. The newspapers incorrectly reported that Mooney had "fled the city" and failed to mention that he had purchased return tickets when he left San Francisco.
None of the witnesses of the bombing identified the defendants in the lineup. The prosecution case was instead based on the testimony of two men, an unemployed waiter, John McDonald and Frank Oxman, a cattleman from Oregon. They claimed that they saw Warren Billings plant the bomb at 1.50 p.m. Oxman saw Tom Mooney and his wife talking with Billings a few minutes later. However, at the trial, a photograph showed that the couple were over a mile from the scene. A clock in the photograph clearly read 1.58 p.m. The heavy traffic at the time meant that it was impossible for Mooney and his wife to have been at the scene of the bombing. Despite this, Mooney was sentenced to death and Billings to life-imprisonment. Rena Mooney and Israel Weinberg were found not guilty and Edward Nolan was never brought to trial.
A large number of people believed that Billings and Mooney had been framed. Those involved in the campaign to get them released included Robert Minor, Fremont Older, George Bernard Shaw, Heywood Broun, Samuel Gompers, Eugene V. Debs, Roger Baldwin, John Dewey, John Haynes Holmes, Oswald Garrison Villard, Norman Hapgood, Crystal Eastman, Norman Thomas, Upton Sinclair, Theodore Dreiser, Sinclair Lewis, Lincoln Steffens, H. L. Mencken, Burton K. Wheeler, Sherwood Anderson, Abraham Muste, Harry Bridges, James Larkin, James Cannon, William Z. Foster, Alexander Berkman, Emma Goldman, William Haywood, William A. White, Carl Sandburg, Arturo Giovannitti and Robert Lovett.
Mooney's defence team complained about the method of selecting his jury. Bourke Cockran pointed out that in San Francisco "each Superior Court Judge places in the box from which the trial jurors are drawn the names of such persons as he may think proper. In theory he is supposed to choose persons peculiarly well qualified to decide issues of fact. In actual practice he places in the box the names of men who ask to be selected. The practical result is that a jury panel is a collection of the lame, the halt, the blind, and the incapable, with a few exceptions, and these are well known to the District Attorney who is thus enabled to pick a jury of his own choice." It was also discovered that William MacNevin, the foreman of Mooney's jury, was a close friend of Edward Cunha, who led the prosecution. MacNevin's wife later claimed her husband was in collusion with Cunha during the trial.
In 1917 the American government became concerned about the conviction and imprisonment of Tom Mooney and Warren Billings and the Secretary of Labor, William Bauchop Wilson, delegated John Densmore, the Director of General Employment, to investigate the case. By secretly installing a dictaphone in the private office of the District Attorney he was able to discover that Mooney and Billings had probably been framed by Charles Fickert and Martin Swanson. The report was leaked to Fremont Older who published it in the San Francisco Call on 23rd November 1917.
There were protests all over the world about this miscarriage of justice and President Woodrow Wilson called on William Stephens, the Governor of California, to look again at the case. Two weeks before Tom Mooney was scheduled to hang, Stephens commuted his sentence to life imprisonment in San Quentin. Soon afterwards Mooney wrote to Stephens: "I prefer a glorious death at the hands of my traducers, you included, to a living grave."
In November 1920, Draper Hand of the San Francisco Police Department, went to Mayor James Rolph and admitted that he had helped Charles Fickert and Martin Swanson to frame Mooney. Hand also confessed that he had arranged for John McDonald to get a job when he began threatening to tell the newspapers that he had lied in court about Mooney and Billings.
Mooney's defence team now began to search for MacDonald. He was found in January 1921 and agreed to make a full confession. He claimed he did see two men with the large suitcase but was unable to get a good look at them. When he reported the incident to District Attorney Charles Fickert he was asked to say the men were identify Warren Billings and Tom Mooney. Fickert said that if he did this "I will see that you get the biggest slice of the reward." Later two witnesses, Edgar Rigall and Earl K. Hatcher, came forward and provided evidence that Frank Oxman was 200 miles away during the bombing and could not have seen what he told the court at the trial of Mooney.
In February 1921 John McDonald confessed that the police had forced him to lie about the planting of the bomb. Despite this new evidence the Californian authorities refused a retrial. After the publication of this new evidence it was generally believed that Charles Fickert and Martin Swanson had framed Mooney and Billings. However, Republican governors over the next twenty years: William Stephens (1917-1923), Friend Richardson (1923-1927), Clement Young (1927-1931), James Rolph (1931-1934) and Frank Merriam (1934-39) all refused to order the release of the two men.
The international campaign to free Tom Mooney and Warren Billings continued. In a survey carried out in 1935 and it was discovered that Tom Mooney was one of the four best known Americans in Europe (other three were Franklin D. Roosevelt, Charles A. Lindbergh and Henry Ford).
In 1937 a group of politicians led by Caroline O'Day, Nan Honeyman, Jerry O'Connell, Emanuel Celler, James E. Murray, Vito Marcantonio, Gerald Nye and Usher Burdick asked President Franklin D. Roosevelt to intercede in the case. When Roosevelt declined Murray and O'Connell introduced a resolution in the Senate calling on Governor Frank Merriam to pardon Mooney and Billings.
In November 1938 Culbert Olson was elected as Governor of California. He was the first member of the Democratic Party to hold this office for forty-four years. Soon after gaining power Olson ordered that Mooney and Warren Billings should be released from prison. Rena Mooney, who welcomed her husband as he left San Quentin, was quoted as saying: "These twenty-two long years have been moth-eaten. Life to me has been something like a cloak. There is little left but the tatters."