Hartlepool have been on the slide but Oldham are moving closer to the promotion places. They dominated much of the game and created enough chances to win by a much bigger margin.
Liddell almost broke the deadlock after nine minutes when he reached a Paul Edwards cross and brought a superb save from Hartlepool keeper Dimitrios Konstantopoulos.
Liddell and Mark Hughes created the next opening for Luke Beckett but the on-loan striker was unable to steer his volley on target.
Oldham opened the scoring on 37 minutes after Paul Warne set them on the attack with a superb crossfield pass to Liddell. The Latics captain crossed from the right and, with Hartlepool appealing in vain for offside, Beckett tapped in from six yards.
Beckett then fired over and was gifted a chance on 41 minutes when Konstantopoulos mis-kicked a clearance and gave him the ball 16 yards out. The keeper redeemed himself with a smart save and also kept out Liddell's stinging long-range free-kick.
Konstantopoulos was left helpless on the hour though when he pulled off a superb block after Liddell had met a right-wing centre from Warne. The ball dropped nicely for Liddell who blasted home from eight yards.
Hartlepool looked dead and buried but they almost pulled one back when Anthony Sweeney broke from midfield and was denied by Chris Day.
Richie Humphreys had a shot cleared off the line before the visitors grabbed their consolation 15 minutes from time. Eifion Williams shot from the corner of the area and saw his effort go in off the inside of the far post for a third goal in three games.
The nearest Hartlepool came to levelling was when Day tipped over Sweeney's shot from the edge of the box.