So I happened to come across a couple of sentence examples on Linguee that truly perplexed me, namely:

„Der Junge wurde bezichtigt, Geld gestohlen zu haben.“
„Er war sicher, bei der Prüfung durchgefallen zu sein, aber das Gegenteil traf zu.“

So my question is: why does the auxiliary verb take the infinitive in these sentences, and when is such a grammatical phenomenon ever used?


Those types of sentences are called erweiterter Infinitiv mit zu and are very frequent in German. Your example sentences just so happen to have modal verbs, but that's just a coincidence.

The full infinitive in your first sentence reads

jemanden bezichtigen etwas zu tun (to accuse someone of doing something)

This already introduces the erweiterter Infinitiv mit zu. If you want to accuse someone of doing something in the past, you may want to use the perfect in German. The perfect is constructed with the auxiliary verb haben and the past participle. This leads to

jemanden bezichtigen etwas getan zu haben

Hence, in full sentence (with a passive construction) this becomes

Der Junge wurde bezichtig, Geld gestohlen zu haben

The full infinitive of the second sentence is

sich sicher sein etwas zu sein (to be sure to be something)

Now durchfallen uses sein to construct the Perfekt. Following the steps above we find

Er war sich sicher, durchgefallen zu sein.

By not using the Perfekt, we have no need to use the auxiliary verbs, so your sentences would read

Er wird bezichtigt zu stehlen.

Er ist sich sicher durchzufallen.

  • Thanks for the help mate. – Jake Apr 9 '20 at 1:13
  • I think durchgefallen zu sein is also a infinitive perfect, in this case of the verb durchfallen, fallen forming the present perfect with the auxiliary sein. – Ralf Joerres Apr 9 '20 at 17:54
  • Isn't that exactly what I said? – infinitezero Apr 9 '20 at 19:14
  • I didn't read the following sentence, sorry. I read 'something' as 'adjective'. Maybe it's misunderstanding. For me, the infinitive of the second sentence ist _ (sich) sicher sein, etwas zu + Infinitv_, and the infinitive can be an infinitive perfect. You can also construct it with an adjective: Er war (sich) sicher, krank zu sein. Here, the infinitive would be sich sicher sein etwas zu sein. That's why I misunderstood it. – Ralf Joerres Apr 9 '20 at 19:31

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