Photo Credit: AFP
The conservative Anez, 54, has been held in pre-trial detention for the last 11 months. She has been on hunger strike, not for the first time, since last Wednesday.
She and another eight former military personnel will be on trial, starting from 9:00 am (1300 GMT).
Anez is accused of unconstitutionally assuming the presidency in November 2019 following the resignation of Morales, who fled into exile following 14 years in power.
Morales quit and left the country in the midst of street protests over his re-election the month before.
The Organization of American States (OAS) performed an audit and found clear evidence of election irregularities.
"I assumed the presidency of Bolivia without asking for it, without looking for it and much less expecting it... with the only mission to call new elections and pacify a country in convulsion," Anez said on Tuesday.
Her lawyer Luis Guillen has accused authorities of bias as the document that opens the trial describes Anez as the "de facto" and "unconstitutional" ex-president.
Guillen has demanded an in-person trial and that witnesses be made to attend for cross-questioning after the public prosecutor's office said it would be submitting only witness statements.
On Tuesday, a group of 21 former Latin American presidents asked the United Nations to visit Anez and investigate potential "abuses of power" in her treatment.
'Massacres'
Another accusation of sedition, terrorism and conspiracy against Anez is still under investigation.
Guillen said the two investigations relate to "the same event" adding that it violates a general principal of law.
He added that "an ordinary court cannot decide what is constitutional."
Guillen said an ex-president should not be tried in a regular court but rather face a trial of responsibilities in congress.
The plaintiffs in the case are the government, public prosecutor and congress dominated by the ruling Movement for Socialism party.
"This is a political trial being carried out by the government of President Luis Arce," said political scientist Carlos Cordero from the San Andres university.
"It's a way of establishing a political sanction for those that dared to be adversaries at a time of crisis for the Movement for Socialism."
Anez is also accused of genocide following complaints made by the families of victims of a police crackdown against protesters in November 2019.
A group of experts commissioned by the Inter-American Commission on Human Rights and the government said 22 people were killed in "massacres" carried out by security forces.
Unlike the other accusations, though, it will be dealt with by congress in a trial of responsibilities.
The report also questioned the independence of Bolivia's judicial system.
Sudden change in results
In October 2019, Morales stood for a fourth consecutive term as president despite the constitution setting a limit of two successive terms.
The election appeared to be heading for a second round run-off until a 24-hour blackout in the live and transparent reporting of results.
When that resumed, Morales had suddenly jumped into a winning lead.
There followed three weeks of protests against his re-election during which time Morales lost the support of the police and military, and fled the country.
Those who would have succeeded him -- all members of his MAS party -- also resigned and fled either abroad or into embassies, leaving Anez -- then vice-president of the senate -- as the highest ranking official left in office.
Congress, which was controlled by MAS, recognized her as interim president despite the lack of a quorum due to a boycott by many members of MAS.
Her sole task was to organize new elections but it took a year for those to be held, in part due to postponements over the coronavirus pandemic.
With Morales living in Argentina, his former finance minister Arce romped to victory.
Anez handed over power in November 2020 and was arrested in March 2021.
