To throw someone under the bus

[poli]

This means to betray someone-or-
to tattle.
Is there a similar Spanish expression.

example: Watch out what you say to him. He'll throw his own mother under the bus if gets him out of a jam.

[chileno]

Vendería a su madre con tal de salir del problema.

(persona muy confiable...) ;)

[ROBINDESBOIS]

In Spain we have more than one sentence for that, One would be :

Te vendería a un gitano. If the others come to me, I´ll be back with you.

[ookami]

"Dar una puñalada por la espalda"? (Stab from the back)

[ROBINDESBOIS]

Dar una puñalada trapera

[sosia]

other "dejarte vendido", when someone leaves you with a big problem and no good outcome.

In Spain it happens a lot :D :D