Elizabeth Dehner Dr . Elizabeth Dehner was a female Human Starfleet officer in the 23rd century . She served in the sciences division aboard the in 2265 under the command of Captain James T . Kirk , during a historic five - year mission that starship undertook . Early History . A medical study into Elizabeth Dehner ' s family history found that esper orientation and abilities were in both her paternal and maternal bloodlines ; however , there was only one case where the tendency for ESP was traced back three generations . She was born on stardate 1089 . 5 , in the city of Delman , and was the daughter of Gerald Dehner . In the 2260s , she had earned a PhD in psychiatry and was the author of a medical thesis on esper - oriented beings . Dehner had been aware of her esper rating ( 089 ) , aperception quotient ( 20 / 100 ) , Duke - Heidelburg quotient ( 256 ) , and general knowledge quotient ( 654895 - 109 ) being better than average in all categories . Her abilities were evident in childhood , displayed in her superiority at guessing game s , reading cards , and other activities . This was , in part , the basis for her vocational training as a psychiatrist . Participation in tests and studies of other related esper - oriented beings were the subject of a thesis published by her in association with the College of Medical Sciences of the Tri - Planetary Academy and was , in fact , the reason for her posting to the Aldebaron colony . Encounter with Galactic Barrier . In 2265 , she joined the crew of the during a stopover at the Aldebaron colony . A member of the sciences division , her assignment was to study crew reaction in emergency conditions . She was aboard when the " Enterprise " went on an initial , fate ful excursion beyond the galactic barrier , a journey that changed Gary Mitchell forever , causing him to develop psionic energy abilities . It changed Dehner , too , but this did not become apparent until much later , at Delta Vega . There , she began to develop abilities like those Mitchell had been displaying . When Mitchell fled captivity , he took Dehner with him , into the hills of Delta Vega . Captain Kirk followed , determined to put an end to the threat posed by Gary Mitchell . Sensing Kirk ' s pursuit , Mitchell sent Dehner to intercept him ; he hoped she would come to his opinion that mortals were highly insignificant . However , she retained enough of her Human ity to be appalled by Mitchell ' s actions and sacrificed her life to weaken Mitchell , an act that allowed Kirk to kill him . Kirk noted in his log that both officers died in the line of duty , since neither had asked for what had happened . ( ) Appendices . Background information . Dehner was played by actress Sally Kellerman . The uniform Dehner wore had one braid for the rank s of ensign to commander ; therefore , her rank cannot be determined from her uniform . Since NBC executives had found the depiction of Vina as an Orion slave girl in ( " Star Trek " s first pilot episode ) too raunchy , the role of Elizabeth Dehner was deliberately much less sexual for the following pilot episode , " Where No Man Has Gone Before " . Herbert F . Solow observed , " " Not even the most conservative of conservatives could characterize the female guest - star role [ of Dehner ] [ . . . ] as being too erotic . " " ( " " , pp . 61 & 66 ) In the revised first draft script of " Where No Man Has Gone Before " ( dated ) , Elizabeth Dehner was described as " " past her mid - twenties , rather tall and slim , with a face that could be beautiful if she cared to make it so . She doesn ' t . She has a normal quota of emotions , but they are carefully controlled and concealed behind a facade of sober intelligence . " " In the final revised draft of the script ( dated ) , the last sentence of that description was eliminated , and the character was scripted as having the middle initial " M " , though this is not established in the episode ' s final version . Another facet that was scripted but isn ' t evident in the installment ' s final edit was that she was to initially appear horrified by Gary Mitchell showing her that , like him , she too had been transformed ( with her eyes having turned metallic ) . Director James Goldstone was involved in casting the part of Dr . Dehner . He remembered , " " We read a number of other actresses for the role [ . . . ] I , along with Gene [ Roddenberry ] and whoever else , did cast Sally , but again , Sally went with [ Mitchell actor ] Gary [ Lockwood ] beautifully . There was a marvelous kind of physicality to her . " " ( " The Star Trek Interview Book " , p . 106 ) Unlike Gary Lockwood , Sally Kellerman had no problems with the silver contact lenses required for the role . ( " " , p . 80 ) She did , however , have a problem with Dehner ' s uniform . Due to embarrassment over the fact that the tight costume was particularly close - fitting around her crotch area , Kellerman was given a " space clipboard " prop that she held close to her , covering up the problem , and was shot from the waist up , whenever possible . Also , because she at first speculated that women of the future would not wear brassieres , she initially suggested that Dehner not wear one , but James Goldstone persuaded the actress to change her mind . ( " " , pp . 83 - 84 ) Kellerman ultimately thought she looked somewhat " pudgy " in the costume . She stated , " " You know , I never had to wear anything like " this " before . " " ( " Starfleet Access " for " Where No Man Has Gone Before " , TOS Season 1 Blu - ray special features ) Denise Okuda cited Elizabeth Dehner as one of the many " strong " and " professional " women characters that " stood their ground " and were often conceived by Gene Roddenberry . ( " Starfleet Access " for " Where No Man Has Gone Before " , TOS Season 1 Blu - ray special features ) Dehner ' s biographical readout listed her age as 21 , as of 2265 ( stardate 1089 . 5 ) , suggesting a birth year of 2244 . It also listed her height as 5 ' 2 " and weight as 116 . However , it was possible that the readout was a medical profile taken during her last examination , when she was 21 , so she could very well be older during the events of " Where No Man Has Gone Before " , as suggested by the script . Given that Kellerman stands 5 ' 10 " tall , Dehner ' s height listing is very much off the mark . Apocrypha . In the alternate reality - set IDW comic " Where No Man Has Gone Before , Part 1 " , Dehner was involved with at one point , a relationship that did not end well . She declined transfer to the when she learned that he was onboard , and thus was not on the ship when they approached the galactic barrier .