[The Squatter of Amon Rûdh]

For me the pivotal moment is here:

Gollum looked at them. A strange expression passed over his lean hungry face. The gleam faded from his eyes, and they went dim and grey, old and tired. A spasm of pain seemed to twist him, and he turned away, peering back up towards the pass, shaking his head, as if engaged in some interior debate. Then he came back, and slowly putting out a trembling hand, very cautiously he touched Frodo's knee - but almost the touch was a caress. For a fleeting moment, could one of the sleepers have seen him, they would have thought that they beheld an old weary hobbit, shrunken by the years that had carried him far beyond his time, beyond friends and kin, and the fields and streams of youth, an old starved pitiable thing.
But at that touch Frodo stirred and cried out softly in his sleep, and immediately Sam was wide awake. The first thing he saw was Gollum - 'pawing at master,' as he thought.
'Hey you!' he said roughly. 'What are you up to?'
'Nothing, nothing,' said Gollum softly. 'Nice Master!'
'I daresay,' said Sam. 'But where have you been to - sneaking off and sneaking back, you old villain?'
Gollum withdrew himself, and a green glint flickered under his heavy lids. Almost spider-like he looked now, crouched back on his bent limbs, with his protruding eyes. The fleeting moment had passed, beyond recall.*

This would appear to be an open-and-shut case. Gollum is on the verge of repenting - his very appearance says so - but Sam wakes up and immediately assumes that he means harm. The moment passes, and the old Gollum returns for good, indicated by the return of the green glow in his eyes: Sam's suspicion has driven him back to evil. However, at this time, on the very stairs of Cirith Ungol, Gollum is already leading his companions to Shelob without a word of warning. Would he have told them of her had Sam not woken thus? Of course this is possible, but it must be remembered that Gollum had many years of wickedness behind him, beginning with the murder of his friend. The side of his personality that Sam calls 'Stinker' is still there, even if it is in abeyance, and in many ways Sam is right not to trust him, even though his mistrust stands between Sméagol and possible redemption. Witness J.R.R. Tolkien on the subject:

The domination of the Ring was much too strong for the mean soul of Sméagol. But he would have never had to endure it if he had not been a mean sort of thief before it crossed his path. Need it ever have crossed his path? Need anything dangerous ever cross any of our paths? A kind of answer cd. be found in trying to imagine Gollum overcoming temptation. The story would have been quite different! By temporizing, not fixing the still not wholly corrupt Sméagol-will towards good in the debate in the slag hole, he weakened himself for the final chance when dawning love of Frodo was too easily withered by the jealousy of Sam before Shelob's lair. After that he was lost.*

I think that the fault lies on both sides, but we can hardly affix a great deal of blame to Sam. Everything he knew about Gollum told him that he was not to be trusted, and he acted with his master's best interests at heart. That he was so very set in his opinion and so rough with their companion is regrettable, but there was so much in Gollum to forgive, and the understanding required to offer it was denied the half-wise hobbit. Such is the nature of tragedy.

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*(1) The Stairs of Cirith Ungol
*(2) Letter #181 (draughts) to Michael Straight

[ July 16, 2003: Message edited by: The Squatter of Amon Rûdh ]