Self-preservation for the ruling class who are starting to feel they might face justice one day. (either real justice or kangaroo justice)
Uhhh... The BN/UMNO lost in May. This is PH, and even though they are led by Mahatir he (face the fact) probably doesn't have long for this world even if he wants to cling to power. If the election promises are true then Anwar will be PM "soon" and his whole message is Reformasi and the end to the institutions that allowed UMNO to establish competitive authoritarianism in the first place. Capital punishment is part that - arrest political opponents on trumped up changes and then this becomes a threat to trade for silence.
