This is the 16234th most frequent Turkish word.
yalanını
"Yalanını" means "his/her/its lie" in English.
In this sentence, 'yalanını' means 'his/her lie' and is used to denote the object of the verb 'caught'.
Onun yalanını yakaladım.
I caught his lie.
Here, 'yalanını' means 'his/her lie' and is used as the object of the verb 'confessed'.
Bana yalanını itiraf etti.
He confessed his lie to me.
In this instance, 'yalanını' refers to 'his/her lie' as the content to avoid, and it forms part of the reason clause for the action.