Nick Reiner has been indicted for allegedly murdering his parents -- Rob and Michele Reiner -- and a special circumstance allegation has been added.

The alleged killer was indicted in Los Angeles on Wednesday. The indictment adds a special circumstance allegation of lying in wait, and it nullifies the need for a preliminary hearing in the case.

Special circumstances can increase potential penalties for Nick if he's found guilty at trial. It's unclear if prosecutors plan to pursue the death penalty, but it opens the door for the D.A. to pursue capital punishment if Rob is convicted.

Reiner's lawyer, public defender Kimberly Greene, declined to comment following the hearing.

As you know ... Reiner was arrested in December after allegedly stabbing both of his parents to death in their West Los Angeles home.

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