In the Courtroom
Before we look at the grammar, let's introduce some key figures you will find in a courtroom (dómstóllinn).
Doubting: efast um að
In Icelandic, verbs that express uncertainty, doubt, or subjective opinions trigger the subjunctive mood (viðtengingarháttur) in the following clause.
To say you "doubt that" something is true, use the middle voice verb efast, followed by the prepositions um að. The verb in the statement you are doubting must be in the subjunctive.
Notice how the verb vera becomes sé (the present subjunctive of er). Other verbs also take their present subjunctive forms, such as segi (from segja) or samþykki (from samþykkja).
Denying: neita því að
Similarly, denying a statement triggers the subjunctive. The verb neita (to deny) governs the dative case. Because of this, you must insert the dative pronoun því before að. The structure becomes neita því að (literally "deny it that").
Doubting or Denying Past Actions
If you are doubting or denying something that already happened, you use a compound tense in the subordinate clause. You combine the present subjunctive of hafa (usually hafi) with the supine (sagnbót) of your main verb.
When the Denial is in the Past
If the act of doubting or denying itself happened in the past, the main verb changes to the past tense (like neitaði). Consequently, the subordinate clause shifts one step further back into the past, using the past subjunctive of hafa (hefði, hefðir, etc.) plus the supine.
