You're assuming the person isn't traveling on a totally false passport, Israeli intelligence has been caught in the past stealing identities of real new zealanders to obtain legitimate, issued by NZ government passports, for instance.
The Russian intelligence offers traveling on fake passports involved in the recent Skripal poisoning case didn't care one whit about the UK's customs face recognition, or omnipresent camera systems, and they were up to something far more nefarious than this.
Ummm...the Russians are on a suicide mission of sort. Do this and stay in mother Russia for the rest of your life, if you don't get arrested. They have a powerful nation state behind them and one that does not extradite its citizens. Even if regime changes, its very unlikely that they will be surrendered due to bad precedent.
1. Face
2. Assumption that the guy fled the country ASAP as soon a he was spooked