HEIDI (short for Holographic Engineering and Imaging Direct Interface) was a Kartaali holographic crewman serving aboard Starfleet’s USS Cantabrian-A from 2374 until at least 2376.
On a mission aboard the Cantabrian‘s support ship USS Determination in early 2376, HEIDI malfunctioned when the Vendoth hacked the Determination’s computer core. As a result, she attacked the engineering crew, killing Lisa Oh before Milami Thall took her forcibly off-line.
Upon the Determination‘s return to the Cantabrian, HEIDI was reactivated. Shocked at being forced to murder Lisa Oh under Vendoth control, she required counseling. (“Howl“)