Correct tense - 'Utter' or 'Uttered'

It is possible that you can use either here, though the sentence is kind of rough. You cannot "see" words that are uttered, and I think the word "access" with regards to intentions is not the greatest choice (perhaps "I cannot know your intentions" or "I cannot perceive your intentions".)

However, in regards to the specific question, it depends on what you mean. If you are making your judgement based on what the person is saying at the moment then the present tense is appropriate, if you are judging them on their past utterance then the past tense is appropriate.

Last night you were really rude to me at the party. I don't know your intentions, I can only consider the words that you uttered.

Here your judgement is based on something said last night, in the past. However,

This conversation is getting out of hand. I don't know your intentions, I can only consider the words that you utter.

Here your judgement is based on something being said at the present time in the conversation you are having right now.

Of course for completeness,

Tomorrow we will really see the truth. I don't know your intentions, I can only consider the words that you will utter.

Here, your judgement hasn't taken place yet. You don't know the intentions now, but you will be able to judge when they utter words tomorrow -- in the future.

So in summary both can be correct, it depends on what you want to say.