Learn Spanish (Spain): Dudo que él me lo justifique. - I doubt that he will justify it to me.

The verb is justificar. In the present subjunctive, we normally swap the -ar ending for an -e. But if we wrote "justifice", the c before an e would sound like a soft "th" (in Spain) or "s". To keep the hard "k" sound from the original verb, we change the c to qu, making it justifique.

Why do we use the subjunctive mood (justifique) here?

The phrase dudo que (I doubt that) triggers the subjunctive. Because the first part expresses doubt and there is a change of subject (from "I" to "he"), the second verb must be in the subjunctive.

Why are me and lo placed before the verb instead of after?

Me (to me) and lo (it) are object pronouns. In Spanish, these pronouns must be placed immediately before a conjugated verb like justifique. Also, the indirect object (me) always comes before the direct object (lo).

The English translation says "will justify", so why don't we use a future tense here?

Spanish uses the present subjunctive to talk about both the present and the future. Since dudo que requires the subjunctive, and there is no future subjunctive tense used in everyday modern Spanish, the present subjunctive justifique covers the future meaning perfectly.