勝手 かって
katteni

Adverb

1. arbitrarily; of its own accord; without asking; voluntarily; willfully; as one pleases; selfishly; by itself; automatically

書類 しょるい勝手 かってにいじられた形跡 けいせきがあった。
shoruiwa katteni ijirareta kēsekiga atta.
The documents were tampered with.