ST. LOUIS -- Prosecutors are investigating a Twitter post claiming that grand jurors hearing evidence in the police shooting of an unarmed black 18-year-old near St. Louis haven't seen enough evidence to justify prosecuting the officer.
The Twitter user claimed in a tweet posted Wednesday that a friend serving on the grand jury said the panel lacked evidence to warrant an arrest of Darren Wilson, the white officer who shot Michael Brown on Aug. 9.
The tweet and its Twitter account were deleted by Wednesday evening. Ed Magee, spokesman for St. Louis County prosecutor Bob McCulloch, said there was no evidence to suggest information in the tweet was credible.
"We just got it this morning also and will be looking into the matter," Magee told The Associated Press.
The AP has not confirmed the identity of the Twitter user.
The grand jury is expected to complete its work by mid-October or early November. The proceedings are conducted in secret, and a juror's sharing of information with outsiders would likely be considered misconduct.
A law professor at Washington University in St. Louis told CBS affiliate KMOV-TV he doubts that a member of the grand jury leaked information about the proceedings.
"These are experienced, seasoned individuals so it's hard for me to imagine that a grand jury would do something like this," Peter Joy said.
The grand jury, which is made up of 12 members, only requires nine affirmative votes to hand down an indictment. Joy said the panel could continue to hear evidence even if one member was removed for misconduct.
"It wouldn't fold up the grand jury unless that person contaminated the rest," Joy said.
Joy said he expects investigators to find the source of the tweet. He also said the presiding judge may ask to meet with each member of the grand jury individually.
Brown's killing sparked nightly scenes of unrest in Ferguson and stoked national debate over how white police officers handle blacks in their communities.
Critics have called on McCulloch to either step aside or ask Gov. Jay Nixon to appoint a special prosecutor, citing concerns about whether McCulloch could fairly oversee the case. McCulloch's father was a police officer who was killed in the line of duty when McCulloch was a child, and he has many relatives who work in law enforcement.
McCulloch, who has been the county's elected prosecutor for more than two decades, could have filed charges himself but chose to take the case to a grand jury to decide whether the use of lethal force was justified.