With increases in migration across borders, age estimation in living individuals of not (reliably) documented identity becomes all the more important. Unfortunately, there are not many age indicators that can be used for this purpose, and human variation requires specific methodical approaches. In this paper, a recently proposed age marker to assess the age around the critical age limit of 18 completed years is tested. The method uses apophyseal development of cervical vertebrae 2, 3 and 4. Here CT scans of a large sample of Turkish individuals (n = 1276) were assessed, and likelihoods of being 18 years at a given stage were calculated. The likelihood of being at least 18 years for stages 0, 1 and 2 were zero or close to zero in both males and females. By the time that stage 4 was reached, the likelihood to be 18 years were between 65 and 70% (depending on the vertebra) in females and 81 and 90% in males. In comparison to South Africans, the Turkish individuals developed earlier, but the likelihoods of being 18 years were lower at stage 4 as some individuals were still judged to be in stage 3 well into their twenties. Although fairly variable, this method is a valuable new addition to the modalities that can be used for age assessment in the living. CT scans seemed to provide good visualization of the structures in question, although in actual forensic cases the high radiation dose may be problematic.