Police pieced together much of their evidence by reviewing footage from about 55 police and private surveillance cameras showing the brothers' movements before and after the attack.
The shift in the investigation came amid intense press coverage and often bitter public debate and stinging skepticism on social media.
Smollett addressed those doubts in a national TV interview and in a strongly worded statement after the brothers were released from custody after questioning by police.
A week before the alleged attack, Smollett told police he received a threatening letter at work. Prosecutors said Smollett staged the attack because he was unhappy with the studio's response to the threatening letter. Chicago police took it a step further, accusing Smollett of faking the letter as well.
Federal authorities are conducting a separate investigation into that letter.
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