〜に違いない (ni chigainai)

Kare wa mainichi osoku made benkyou shite iru kara, tsugi no shiken ni goukaku suru ni chigainai.

Since he studies late every day, he is sure to pass the next exam.

Kagi ga nai. Dokoka de otoshita ni chigainai.

My keys are gone. I must have dropped them somewhere.

Kanojo ga tsukutta ryouri dakara, oishii ni chigainai.

Since she made this dish, it must be delicious.

Kore hodo ookina purojekuto o makasarete, kare wa taihen ni chigainai.

Being entrusted with such a big project, it must be very tough for him.

Hannin wa, genba no joukyou o yoku shitte iru jinbutsu ni chigainai.

The culprit must be someone who knows the situation of the crime scene well.

Renraku ga mattaku nai no wa, nanika toraburu ga atta ni chigainai.

Having no contact at all means there must have been some trouble.