Complex sentence: As such, the individual effectively allows criminals to carry out a crime despite possibly being able to stop them, either directly or by contacting the authorities, thus making the individual a de facto accessory to the crime rather than an innocent bystander.
Split into simpler sentences: As such, the individual effectively allows criminals to carry out a crime despite possibly being able to stop that person--either directly or by contacting the authorities. The offender is a de facto accessory to the crime; rather than an innocent bystander.