Accomplice
noun
Someone who does crime together with you is your accomplice in crime. It's best to "take care of" these before the coppers get to them.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
共犯者は国外にいる可能性が高いそうだ。
They say the accomplice is most likely out of the country.
共犯者の息子は、一昨年の一月に生まれました。
My accomplice's son was born in January of the year before last.
あの共犯者は、まさに飛んで火にいる夏の虫だったな。
The accomplice was indeed like a bug that flew into the fire in summer.