How did the Jackal kill silently?

Question

In The Day of the Jackal, the Jackal uses some technique to kill people silently without any struggle:

• He kills complacent Colette de Montpellier just by kissing and gently holding her for several seconds: she passes out and never wakes up;
• He kills Jules Bernard (a gay man picked up at a Turkish bathhouse) just by approaching him in the kitchen and doing something to him behind the wall — again, just for several seconds, without any struggle or noise whatsoever;
• In the hotel lounge where he chats up Colette de Montpellier, an old lady is later found dead in her chair which draws the attention of all staff. He uses that moment to look up Colette's room number in the guest register.

I presume that all could be done with some sort of substance applied to the victims' skin. But the movie did not make it clear to me.

So, how does he do it?

Answer 1

I think you are over-analysing here.

Certainly he kills Collette silently, apparently by compressing her carotid artery so that blood is stopped from reaching her brain.

In the novel the death is somewhat more violent...

The lack of any answer from the Jackal gave her the answer. She made a rush for the door. He caught her easily and hurled her back across the room on to the bed, coming after her in three fast paces. As she bounced on the rumpled sheets her mouth opened to scream. The back-handed blow across the side of the neck into the carotid artery choked off the scream at source, then his left hand was tangled in her hair, dragging her face downwards over the edge of the bed. She caught a last glimpse of the pattern of the carpet when the forehanded chop with the edge of the palm came down on the back of the neck.

As for Jules, we do not see the manner of death but since the sound of the television drowns out any sound we do not know that the kill was silent. The Jackal is an expert assassin and would know any number of techniques to kill in such a manner, but the novel indicates that he strangles Jules

Bernard, who was sitting on the sofa, turned round and looked up. The last thing he thought was that the announcer had not been right, for he had said Schulberg’s eyes were blue; but the eyes looking down at him from behind the steel fingers that gripped his throat were grey...

The Day of the Jackal - Frederick Forsyth.

As for the old lady there is no indication that the Jackal had anything to do with the old lady's death, he merely takes the opportunity for access the register in the confusion that arises.