I'm editing a paper and came across a sentence which uses an ellipsis to separate the main idea from a restatement as follows:
The suspicion that the butler committed the murder was just that... a suspicion.
My editing experience tells me that it would be better to use a colon:
The suspicion that the butler committed the murder was just that: a suspicion.
However, I cannot find any definitive justification for this, and would like to know if there is a rule or guideline for this case.
My impression is that the ellipsis is better suited for ideas and lists that trail off (such as a moment in literature that is meant to linger or fade), whereas the colon in this usage is intended to sharpen or focus the reader on the intended upcoming point.
Is the colon the correct choice for this usage? Note that this example is over-simplified and the context is in technical writing of an instructional nature.
A similar question has been asked, but does not consider ellipsis usage.