Trust is not a necessary condition to forgive. As a moral virtue, forgiveness is: a) a conscious awareness that one is trying to be good to the one who was not good to you; b) a softening of emotions from deep anger to compassion, and c) actions that express kindness, respect, generosity, and love toward an offending other(s). This does not necessarily mean that the kindness occurs directly toward the other because reconciliation and forgiveness differ. You can say a kind word to others about the offending person without being in direct contact with the one who offended you, if the other’s behavior is dangerous for you. Forgiveness is unconditional (occurring whenever the forgiver chooses) whereas trust is earned as offending persons show, by genuine remorse and repentance, that they have changed their hurtful behavior. You can forgive and wait on the issue of trust.
For additional information, see: Forgiveness Defined.