Breakdown of El jefe me aseguró que quería interrogarlo porque había visto el asesinato.
ver
to see / to look / appear
porque
because
querer
to want
que
that / than
Questions & Answers about El jefe me aseguró que quería interrogarlo porque había visto el asesinato.
Why did the original statement change to había visto instead of just using the preterite?
This sentence is an example of reported speech. The boss originally said I saw (vi) or I have seen (he visto). Because we are reporting this using a past-tense reporting verb (aseguró), those past actions shift one step further back in time into the past perfect tense: había visto (he had seen).
Why does the sentence use the imperfect tense quería rather than the preterite quiso?
Can the pronoun lo in interrogarlo go anywhere else?
Yes! When working with a conjugated verb followed by an infinitive (like quería interrogar), you can either attach the object pronoun to the end of the infinitive (interrogarlo) or place it directly before the conjugated verb (lo quería interrogar).