Premeditation was the act of contemplating or planning a crime before committing it. Premeditated crimes, particularly murder, were often seen as more heinous due to their being plotted beforehand. This could lead to a stiffer sentence.
In 2367, Sabin Genestra accused Simon Tarses of having premeditatively lied about his Romulan paternal grandfather when enlisting with Starfleet. (TNG: "The Drumhead")
In 2377, Neelix noted that some of the criminals convicted under the Nygean legal system were not executed or punished, yet Joleg received a death sentence. Joleg explained the discrepancy as being due to their practice of Vekto Valek K'Vadim. (VOY: "Repentance")