Mackenzie Shirilla Poses For Prison Photo Shoot While Dealing With Legal Setback

Mackenzie Shirilla is sharing a new photo from behind bars ... along with a positive message after suffering a legal setback.

Despite being locked up, Mackenzie's supporters are using her Instagram account. In a recent post, they uploaded a snap of her from prison, explaining she's "trying to do better every day and holding on to hope" ... despite a recent court decision denying her request for post-conviction relief.

Mackenzie's team explained the denial wasn't based on the substance of her claims. Instead, they said the filing was rejected because it was submitted one day past the deadline.

The post claims her appellate attorney missed the filing deadline and blames the leap year ... and they believe the mistake amounts to ineffective assistance of counsel.

Despite the setback, Mackenzie and her family plan to continue pursuing every available legal avenue in hopes of having her arguments heard in court.

Mackenzie's account also urges supporters to keep spreading awareness for her case and to sign and share an online petition seeking what it describes as a "fair re-trial."

As we've previously reported ... Mackenzie is currently serving a prison sentence after being convicted in connection with the 2022 crash that killed her boyfriend Dominic Russo and their friend Davion Flanagan.