The phrase "are utterly convincing" is correct and usable in written English.
You can use it when describing something that is very persuasive or believable.
Example: "The arguments presented in the debate are utterly convincing, leaving no room for doubt."
Alternatives: "are completely persuasive" or "are highly believable.".
La gaviota is marred by its obtrusive morality and slow pace, but its lively, sympathetic presentations of country people and their conversation are utterly convincing.
On the other hand, Ms. Martin and Mr. Cooper, the adult actors playing Lyra and Will, are utterly convincing in charting their characters' developments into maturity.
Much of the acting, however, is first-rate: Jane Horrocks is excellent as Ella, by turns ferocious and cowed, and the actors playing the children are utterly convincing.
The pages she includes in "Ghostwalk" from Elizabeth Vogelsang's fictional manuscript on Newton, replete with footnotes and illustrations, are utterly convincing.
Both are utterly convincing assaults on the ideals, ideologies, delusions and even the engineering of the Silicon Valley elites that aspire to remake the entire world and its inhabitants as machine-readable code.
While her Panamanian characters are utterly convincing, her prose reads as if it grew up drinking water that had been fluoridated with traces of John Updike and Ann Beattie.
Both men are serving prison sentences at HMP Swansea for violent crimes and both are utterly convinced that their lives will be very different when they are released.
Been there, done that: The amazing thing is the way men who know neither theory nor the history of previous crises are utterly convinced that they know what to do in our current crisis; and how their confidence in their prescriptions has been unaffected by the fact that they have been wrong about everything so far.
A human being will never be a lump of clay that can be moulded to fit the exact formulation of a text; and if you are utterly convinced you going directly to paradise it is not unreasonable to want to squash underfoot like a piece of rotten fruit anyone that stands in your way.
And then there are people who are utterly convinced of their own destiny in terms of success.
Sincere parents, who love their children, but are stuck with a literal reading of badly translated verses taken out of context, are utterly convinced they are doing the right thing.
