remember that gassan had diplomat immunity and he couldn't be touched by American justice. Maybe the lab boys told this to columbo but Clumbo needed more evidence for an arrest so he used the king's influence to nab him. At the end he setteled for American justice instead of his own country's justice. This was a very delicate case and good of been easily dismissed if Columbo jumped the gun.

That is how I understand this episode

It's been a while since I've seen this episode (though it ranks among my favorites), but I'm thinking the murderer believed his immunity would save him from being held accountable--so he needn't fret over incriminating evidence.

Maybe since he had "bear hands", the lab boys couldn't identify the fingerprints.

hahahaha :D