Cyrus Bernard Maina Njuguna, along with his cousin, John Njuguna Waithira, was arrested on October 24 in connection with Ms Maina’s death, Nine News reports.
A magistrate has since ordered for the two men to be released after police did not lay any charges.
Ms Maina was shot in the relatively wealthy suburb of Karen, Nairobi, at around 10am on October 19 by men on motorbikes, after she had dropped one of her two young sons at a friend’s house.
But Mr Njuguna’s lawyer said his client was not in the area where Ms Maina was shot, the ABC reports.
"There is evidence that is capable of corroboration by many people, as many as 10, that Cyrus was in his office at the time that the murder took place," lawyer Wilfred Nderitu explained.
Ms Maina’s lawyer had previously called for investigations into the motives behind Ms Maina’s death amid revelations that she had taken a restraining order out against her estranged husband in April.
“She required a restraining order against the husband for constantly stalking, approaching her place of work and as well as the residence,” Kingori told the ABC. “It is important for them [Department of Foreign Affairs] to keep on pushing until it is certain as to what caused her death.”
“The shooting happened when she was kneeling and someone was standing,” he added.
Ms Maina was originally from Armidale in country New South Wales and was in Kenya working as the head teacher at Nairobi’s Hillcrest Preparatory School.