Kriminallhauptkommissar Semir Gerkhan is the indisputably recognised star of the Alarm für Cobra 11, and is played by Erdogan Atalay.
First appearing in the first season's third episode alongside Frank Stolte, after the death of Ingo Fischer, Semir has remained in the cast for all seasons up to those currently in production in Germany, while at his side alternating several colleagues, all of whom soon become his friends.
Semir is a character very much appreciated by the others in the series, in that he keeps a calm composure under pressure.
A distinct trait that separates him from most of the other characters is that he is a family man, retaining an undying loyalty to caring for his children and his wife, Andrea Schäfer.
Often, he has to calm his rowdy colleagues, such as André Fux. Only in a few cases Semir can not keep calm: in the episode of Tom's death ("Life or Death"), he planned to threaten some people who have to deal with the death of his colleague. In "On Your Own," however, he must ensure justice for the murderer of Chris (a mafia leader known as Sander Kalvus); he tackles this case with much more determination and fury than he did in "Life or Death", to the point where he nearly kills Kalvus. In "Deadly Decision", he is forced to kill Ben if he is to see his family again, which terrifies Semir, to the point where he nearly committed suicide for that. He then shoots Ben at the top of the building, revealing his "death". However, Ben comes back to save the Gerkhans, and Semir reveals that the shot, where he used a blank-firing replica of his service pistol, was only a blank to deceive the gangsters and save his family as he severely injures Steffen Raiser as a reminder to never come after him again. He then exits prison, joyful to see his partner and his family are okay—especially that of his wife, Andrea. In all other cases, however, he thinks before taking any action.
He is unafraid of showing his Turkish origin, shown in several episodes throughout the series; a prominent example is when he yells at a tow truck driver in said language as he chases after a car bomb.
Following the events of Season 34, Semir comes across as disgruntled and depressed. In "Revolution", he mercilessly lashes out at Andrea's boyfriend, even as he is barely acquainted with him. He even starts to become more vindictive and aggressive towards suspects, having pistol-whipped his to-be partner Alex Brandt whilst chasing him on a train. Those murderous traits start to wane months after his divorce with Andrea, but resurface in his amnesiac state during an undercover operation, to the point where he nearly killed Paul Renner, his most recent partner.
Semir has also been recognized for driving his generic undercover patrol car: the BMW 3 series, which had alternately changed over the years, from the car itself (323i E36, 325ts E36, 328i E36, 330i E46, 330i E90, 320si E90 M-Sport, 320d F30, 328i F30 M-Sport) to the license plate number (HVL-S 199, UB-E 438, B-PV 185, NE-DR 8231, NE:DR 8231, D:BM 3308). Semir had also owned and used numerous exotic cars off-duty, but has had terrible events happen to them (BMW M735i wrecked, Ferrari F355 Spyder stolen).