Attorneys for three alleged members of a powerful Southeast Washington drug gang told jurors Wednesday that prosecutors relied too heavily on tainted witnesses and presented insufficient evidence to justify convictions on a slew of charges, including murder.

The comments came during closing arguments in a high-profile trial that started in late January and could be in the hands of jurors by the end of the week. Prosecutors allege that the men — Mark Pray, 30, Kenneth Benbow, 31, and Alonzo Marlow, 31 — conspired to operate a violent drug gang out of the Barry Farm public housing project in Southeast D.C.

Prosecutors have charged Pray, the alleged ringleader, in three slayings, including the April 2009 shooting of Crystal Washington, a 44-year-old mother whom prosecutors said was targeted because she was a witness in a drug case.

Since the trial started Jan. 30, prosecutors have presented testimony from former gang members, recordings from wiretaps, Pray’s Facebook postings and what they have described as incriminating letters found in his cell. They have introduced data from a Global Positioning System-enabled ankle bracelet that authorities said linked Marlow, whom they have accused of being Pray’s “enforcer,” to the slaying of Washington and that of a 20-year-old rival dealer in January 2010.

Defense lawyers on Wednesday attacked the evidence, saying it is more ambiguous than prosecutors suggest. They also questioned the reliability of prosecution witnesses, particularly former gang members with criminal records.

“The evidence falls woefully short in this case,” said Robert L. Jenkins, who represents Benbow. “The government is supposed to be burdened with proof.”

Jenifer Wicks, one of Pray’s attorneys, focused her attacks on a key prosecution witness whom she argued had a strong motive to have Washington slain. In September 2006, Washington and a number of others, including Pray, were arrested inside her Barry Farm home by police who found guns and drugs while responding to a 911 call for “unwanted guests.”

Washington later pleaded guilty and agreed to testify for prosecutors at the trial of Pray and three others in D.C. Superior Court. One of his co-defendants, Marvin Benton, testified last month that he tipped Pray to Washington’s whereabouts. A short time later, Washington was slain, and the criminal case against Pray, Benton and the others was dropped. Prosecutors allege that Pray conspired with Marlow to have the witness killed.

Wicks said Pray had nothing to do with Washington’s slaying and was confident he was going to be acquitted. On the other hand, Washington was the key witness against Benton, and he benefited from her death, Wicks said.

“You can’t believe him,” Wicks told jurors, adding Benton had a long history with Washington and turned the woman back onto drugs. “He concocts a plan that will help him beat his own case.”

In March 2010, Pray, Benbow and Marlow were arrested; they are among 13 people indicted on charges of being part of the gang. Six defendants have pleaded guilty. The dispositions in cases against four others could not be determined from court records.

Staff writer Del Quentin Wilber contributed to this report.