Already out of finals contention, the Saints were seeking a response to their thumping 85-point loss to Brisbane and Marshall kicked three goals to help deliver a 15.9 (99) to 7.9 (51) win at Marvel Stadium on Sunday.
St Kilda (9-12) sit 14th while injury-ravaged Richmond (2-19) are last, behind North Melbourne on percentage.
The victory also ensured St Kilda's week ended on a high note, after they faced scrutiny and supporter backlash following talent manager Graeme Allan's meeting with disgraced ex-North Melbourne player Tarryn Thomas.
On Thursday the Saints confirmed they would not bid to recruit Thomas, after coach Ross Lyon had refused to answer questions about him.
Arguably St Kilda's most influential player, Marshall took on Toby Nankervis and kicked three goals, along with registering 25 hitouts, 11 marks and 23 disposals.
Gun midfielder Jack Sinclair (29 touches) was typically prolific, as was intercepting defender Josh Battle (28 disposals, nine marks), while Cooper Sharman (two goals) and Tim Membrey (three goals) hit the scoreboard.
Tim Membrey soared for the Saints, with three goals. (Scott Barbour/AAP PHOTOS)
Richmond gun Daniel Rioli (36 disposals, 10 marks) showed off his class throughout, and midfielders Tim Taranto, Sam Banks (25 disposals apiece) and Jacob Hopper (28 disposals) were busy.
Young tall Jacob Bauer kicked two goals, along with Hugo Ralphsmith and Shai Bolton.
Saints young gun Mattaes Phillipou (illness) withdrew before the first bounce, with midfielder Paddy Dow recalled in his place.
The first quarter proved an arm-wrestle, but Marshall stepped up, with his late goal from long range giving the Saints a six-point lead at the first change.
St Kilda led by 25 midway through the second term via an unanswered run of four majors, but the Tigers fought their way back into the game, trailing by 14 points at half-time.
The Saints absorbed Richmond's pressure and steadied in the third term to take a four-goal lead into the final quarter.
Marshall received a free kick and kicked his third early in the term and the Saints didn't look back - ultimately kicking the final six goals of the game.
St Kilda finish their season with games against Geelong and Carlton at Marvel Stadium, while Richmond play Hawthorn, then Gold Coast, at the MCG.
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