passive

allege是可以用that或用to-infinitive
第一句，因alleged是過去動作，而he had a villa只是簡單過去式，故可以寫成
He was alleged to have a villa就可以
若寫成He was alleged to have had a villa就＝He was alleged that he had had the villa.
而你第二句就非常正確
He was alleged to be the killer.
希望幫到你！

1. People alleged that he had a villa. (Past tense sentence)
(rewrite the above sentence by beginning with "He".)

2. He was alleged that he had been the killer. (Past tense sentence)

If the tense of the sentence is simple past tense, you should use present perfect tense in the passive sentence. If the tense of the sentence is present perfect tense, you should use past perfect tense in the passive sentence.

Hope I can help you!

2009-03-22 17:19:18 補充：
If the tense of the sentence is present tense, you should use past tense in the passive sentence.

If the tense of the sentence is future tense, you should use past future tense in the passive sentence.

e.g. He will kill Tom tomorrow. --> Tom would be killed by him the next day.