Usage example in [a BBC News story][1]:

>What of the late politician's love life? Even admirers used the epithet "womaniser" in regard to him.<br /><br />
However, the Ukrainian model less than half his age (he was 55) who was with him when he was shot on Friday night could say little about the attack.<br /><br />
Anna Durytska, who was unhurt, told Russian media she **had not seen** the killer, who **had struck** from behind. All she **had seen**, she said, was a light-coloured car which quickly drove off. Into the dark.

Could you please explain to me why in this particular case the author opted for a set of past perfect verb tenses instead of sticking with the simple past tense? To me, it sounds like if we changed all the verbs in the example above to simple past tenses, the sentence would still sound equally correct tense-wise. Don't you think so?

>Anna Durytska, who was unhurt, told Russian media she **didn't see** the killer, who **struck** from behind. All she **saw**, she said, was a light-coloured car which quickly drove off. Into the dark.

  [1]: http://www.bbc.com/news/world-europe-31693234