The death of navy captain Rafael Acosta came on the heels of a visit by the United Nation's human rights chief Michelle Bachelet to investigate rights violations ranging from extrajudicial killings to forced disappearances.
The lawyer added that the suspects will be tried for the murder of an officer, "ignoring the fact of torture".
Acosta's wife, Waleswka Perez, earlier on Monday demanded that the government hand over Acosta's body so it could be inspected.
"I urge the authorities to conduct an in-depth investigation - including an autopsy meeting global standards - that is both independent and transparent", she said.
Without referring to the mistreatment allegations, Attorney General Tarek William Saab, who is close to Mr Maduro, announced an "objective, independent and impartial investigation" following the officer's death.
Acosta, who retired from active service a decade ago, was arrested by Venezuela's Military Counter-Intelligence Command (DGCIM) on Wednesday on charges of terrorism and sedition, in connection to a purported coup plot revealed by Communciations Minister Jorge Rodriguez that same day.
Three people familiar with the talks between representatives of Venezuela's President Nicolas Maduro and the United States backed opposition leader Juan Guaido, are reported to have told the Associated Press about the planned talks.
Acosta was detained on June 21 and his whereabouts were unknown before he was brought before a military tribunal on June 28 and accused with others of plotting to overthrow and assassinate Maduro.
"Despite providing him with the appropriate medical attention, he died", the statement said.
According to a statement by Venezuela's Defense Ministry, Acosta was presented before a military judge at Caracas' Fort Tiuna military base on Friday when he reportedly fainted, prompting the judge to order his immediate transfer to the health facility.