tenses - Going back and forth in time gramatically?

The sentence(s):

The ice breaks beneath them, and they are stuck in their car while it is being filled with ice-cold water. Dawn’s mother had tried to convince Sam, Dawn’s father, not to go on the trip as she suspected it would be dangerous. Sam simply shrugged off her concerns. Should Dawn’s mother have acted differently? Moreover, is it fair that Dawn’s mother may blame herself for the accident?

My question is whether it is correct for me to write "Suspected" instead of "suspects", "shrugged" instead of "shruggs" and "had tried" instead of "tries", the thing is: the story goes back and forth in time, should the words then be in past tense or present tense? It sounds wrong when they are in present tense, I am not quite sure...

Answer

There's nothing inherently wrong with referencing a past event partway through a present-tense narrative, as it clarifies the situation. If I were writing something like this I would probably start a new paragraph when the tense switches to make it more distinct from the rest.

So on that note, you're quite right to use the past tense for those verbs; the reason it sounds wrong when they're in present tense is because it is wrong.

I would even go so far as to recommend saying "Sam had simply shrugged off her concerns" to make it clear that this also happened at the same time as she was trying to convince him, but is now being referenced in the present.