I don't know in his personal case if he is lying. However, you can get to what the probability of a random applicant for an asylum being truthful very easily. You just need a good estimate of the % of migrants that had to flee gangs or other risk of death (gangs that are still in control of their communities), then compare that to the % that claim they had to flee for those reasons, then subtract.

I don't know what that % is, but we have courts that are deciding these cases every day. The actual court cases are more complex to analyze because lack of adequate council or other factors might influence outcomes. However, of people who attend their interview, about 44% are determined to not have a credible fear.