A What???

From the Detroit Free Press:
A design and engineering firm being sued by Wayne County for massive cost overruns at the new jail project is firing back, saying incompetence by county officials and turmoil among the county's staff are responsible for wasting millions of dollars and stalling the project for more than a year.
In more than 700 pages of court documents obtained by the Free Press, lawyers for AECOM, the jail's design and engineering firm, say the county — not contractors — is to blame for the fiasco that has resulted in investigations, criminal charges and lawsuits and likely helped sink the political career of Wayne County Executive Robert Ficano....
The lawsuit highlights one of the costliest local government boondoggles in Michigan history. Originally pegged at $300 million, the project was halted last year as cost estimates soared to almost $400 million. A one-man grand jury indicted three people for their roles in the project, and the project helped seal the political demise of Ficano, who received just 6% of the vote in his re-election bid.  http://www.freep.com/story/news/local/michigan/wayne/2014/10/26/wayne-jail-overruns/17916211/
A 1 man grand jury?
How exactly can 1 person supposed to be a jury?
How can they deliberate with themselves?
Ok, if the person is a judge or a DA, I can see that but a 1 person grand jury???
Doesn't seem to be constitutional to me.