Past participle of sehen in Lesson 9.8

This lesson is on irregularities the präteritum, and has a sentence in the perfect as a comparison.  The sentence is:

Sie hat die Leute wegfahren sehen. The translation is 

“She saw the people drive away.” with a literal translation “She has the people away+to drive to see.”

Why is the infinitive of sehen used here rather than the past participle gesehen, since hat is the auxiliary verb?

Is it because the sentence ends with two verbs?

Hi Peter--252, 

Thank you for your question!

The infinitive is used here because it is a so-called double infinitive construction. This means we have to use the infinitive of sehen instead of a past participle because it is being used with another verb ("wegfahren"). You can use the past participle when it's not used with another infinitive, such as

“Ich habe die Leute gesehen.” - "I saw the people."

Hope this helps!

Viele Grüße

Julia

Hi Julia,

Thanks for the prompt reply.

Now that I've read it I think that I might have read that rule before during the course (I'd forgotten), possibly in a previous lesson. Or perhaps in a lesson before they were reorganised.

Anyway, that's one point I won't forget again!

Viele Grüße.