Ramsey-Guy is accused of turning off the water and not logging the action nor informing other officers he had done so.
The charges announced by the Milwaukee District Attorney's Office come nearly a year after jurors recommended jail staff should be liable after prosecutors presented them with evidence.
Police detectives asked Evans in a questionnaire during their investigation whether there was any documentation showing whether the water was turned off the whole time or intermittently.
A criminal complaint says that Evans knew about critical video surveillance but lied about her knowledge to investigators in order to protect her job.
The charge is a felony that is punishable by up the 3 1/2 years in prison. The document Evans signed off on answered that "there is no documentation indicating this". However, prosecutors say Evans was aware of the tape and that it showed the water to Thomas' cell is turned off and never turned back on again.
"But to a certain extent that's what brings us here as well, and that is Mr Terrill Thomas shared that same presumption and expectation when Mr Thomas was brought into custody is that he would be kept safe".
Thomas was arrested on April 15, 2016 and then charged with reckless endangerment and firearms violations after he fired shots in a local casino, court documents said.
Jail policy states that an inmate should have 24/7 access to water in their cell. Former Sheriff David A. Clarke Jr. was in office at the time of Thomas' death but has not commented on how Thomas was treated, the Journal-Sentinel reports. He was transferred to the disciplinary unit and that's when Meadors ordered Officer Ramsey-Guy to turn off the water to Thomas' cell until "he behaves".
While Meadors and Ramsey-Guy are being charged for neglect in relation to Thomas' death, Evans is accused of interfering with the investigation for allegedly destroying video surveillance taken during the week Thomas was deprived of water by allowing it to be recorded over. In the month following Thomas's death, the jail disciplined two other inmates by denying them water for a period of time, according to Monday's criminal complaint against Ramsey-Guy and the other jail staffers.
One of the cases happened a week after his death.
In November 2016, a former inmate at the Milwaukee County Jail filed a lawsuit alleging that her baby died after guards there refused to give her help as she went into labor.
"I will be very strong on my decisions if indeed those documents support what I believe they're going to show", Schmidt said.
Sheriff Schmidt said the accusations against his employees were "horrific" and that "my heart bleeds" for Mr. Thomas's family. "To the family, I have nothing but deepest sympathies for their loss".
All three are now free on signature bonds following court appearances Monday. He said, however, that charges are possible later against the company the jail contracts with to provide health care to inmates.