Leinster (16) 31
Tries: McWeeney 2, Warner
Cons: O'Meara 2
Pens: O'Meara 4
Scarlets (3) 20
Tries: Selley, Boobyer
Cons: B Davies 2
Pens: G Bowen 2
Leinster made it four wins in a row in their final home Celtic League fixture of 2003, as tries from Australian centre Christian Warner and wing John McWeeney saw them hand the Scarlets their first loss on their travels.
Two McWeeney tries in three second-half minutes killed off the Scarlets' challenge, with scrum-half Brian O'Meara contributing 16 points with the boot.
It was a lively opening from both sides with Leinster, backed by a slight breeze, pinning the visitors back into their 22 after three minutes.
A high tackle from wing Salesi Finau gave O'Meara his first penalty success from in front of the posts.
Gareth Bowen replied barely 60 seconds later from inside the Leinster 10 metre line, for what proved to be the Scarlets' only score of the first half.
Gary Ella's side got the crucial score in the 27th minute when Warner arrived onto a flat pass from David Quinlan to outpace Barry Davies to the Welsh line.
O'Meara converted and a third success with the boot gave the home side a 13-3 lead after half an hour.
A third penalty from O'Meara went straight over in the fourth minute of injury time, before Bowen brought the Scarlets back to within 10 points after four minutes of the second half with a penalty.
A moment of controversy followed with the sin-binning of Leinster lock Ben Gissing and Scarlets' prop John Davies for infringing, only for Davies to rejoin the action a minute later.
Referee Rob Dickson failed to notice but yellow-carded lock James Griffiths three minutes later, and with play continuing, McWeeney scored his brace on 54 and 56 minutes.
The Welsh side scored a consolation try through centre Tal Selley, his fourth of the season coming from close range in the 72nd minute.
The Scarlets pushed for another score late on and Ian Boobyer crossed in stoppage time for a try converted by full-back Barry Davies.
Leinster: Gordon D'Arcy; John McWeeney, Christian Warner, David Quinlan, Gary Brown; Matthew Leek, Brian O'Meara;
Emmett Byrne, Gavin Hickie, Niall Treston, Aidan Kearney, Ben Gissing, Niall Breslin, Shane Jennings (capt), Des Dillon. Replacements: Peter Coyle, David Blaney, Ciaran Potts, Niall Ronan, Shane Whelan, Peter McKenna, Daragh O'Shea.
Scarlets: Barry Davies; Richard Rees, Tal Selley, Matthew Watkins, Salesi Finau; Gareth Bowen, Mike Phillips; Phil John, Aled Gravelle, John Davies, James Griffiths, Adam Jones, Vernon Cooper (capt), Ian Boobyer, Emyr Lewis.
Replacements: David Maddocks, Adam Yelland, Bryn Griffiths, Gareth Williams, Dale Burn, Ceiron Thomas, Lee Bryne.