This paper presents statistical data for the fundamental frequency of 100 young male speakers of Standard Southern British English producing spontaneous speech under cognitive stress. The material comes from the new X database, for which subjects underwent a simulated police interview. The distribution of F0 in a large homogenous group of speakers is of forensic significance since it provides a framework for understanding the significance of F0 measurements in casework. Long-term F0 for the 100 speakers yielded a mode of 102.2 Hz, a mean of 106 Hz and a median of 105 Hz, and had a near-normal distribution. We demonstrate the limitations of F0 as a discriminatory feature for the majority (60%) of our speech group, which fell within a narrow window of 20 Hz. Conversely, we see the forensic implications for recordings where F0 falls outside this window.