Continuity mistake: When MacGyver drives the forklift into the car one of the forks goes through the windshield. When the shot changes it is now out of the window. You can see the broken windshield where it had gone through.
The Prodigal - S1-E9
Continuity mistake: When the car breaks down and MacGyver backs up the tow truck he hits the Fed's car, but in the next scene after he gets out of the truck it is feet away, he never moved the truck.
A Prisoner of Conscience - S1-E21
Continuity mistake: When Pete steals the drugs, he puts them in his pocket and drops a bag right near the door, but when the doctor comes in and finds it it's much farther away from the door than where he dropped it.
Continuity mistake: When Tommy is escaping into the mountains to try and help, a small bit of his jacket tears off onto a tree branch. MacGyver later sees it, but the branch that the torn piece is on looks entirely different. (00:21:10 - 00:22:10)
Jack of Lies - S2-E6
Continuity mistake: When MacGyver et al. spot the car they will use to escape, the headlights are clean and white. After the commercial break, they are much dirtier and the dirt is only on certain precise spots on the headlights. (00:33:15 - 00:35:25)
Continuity mistake: When the Golden Eagle is shot with the crossbow by the man, It goes through it's wing. Later when MacGyver comes to try and take it out, it is in a different position on the bird. It is not through the wing anymore. (00:07:25 - 00:09:15)
Continuity mistake: While running on the mountain, the stunt double is wearing a white shirt while MacGyver is wearing a blue shirt.
Continuity mistake: During the car chase through the desert, the rear view mirrors on both cars disappear and reappear repeatedly.
Continuity mistake: The bullet hole fired into the red Cadillac by the bad guy later disappears.
Continuity mistake: In the opening scene, the hitmen's car loses a hubcap as it chases mobster Tony. In the following shots, however, all four of the car's hubcaps are back in place.
Continuity mistake: Throughout the desert car chase, the bad guys' Chrysler hood ornament and various hubcaps on different wheels of their car disappear and reappear multiple times. The car is dirty and then clean too.
Continuity mistake: When Mac and the ambulance are running through the checkpoint at the hospital exit, when you first see the shot the stop bar is already broken off on his side of the road, in the next shot they are driving through the bar breaking it off.
Continuity mistake: MacGyver appears to be a novice at mountain climbing, but in the very first episode he mountain climbed like a professional.
Continuity mistake: In the scene where the gang are chasing after the two kids, it is raining and the street is wet. They stop chasing and turn around when they see a police car go by. In the first shot of the police car, the street is completely dry. (00:05:45)
Continuity mistake: The episode begins with MacGyver's Jeep having a blowout and going off the road, however, when we see the overturned Jeep, all 4 tires are inflated. (00:01:45 - 00:02:15)
Continuity mistake: Here as in every episode where MacGyver's Jeep appears, it's the '80s model with the square headlights. When we see him fixing the Jeep after the wreck, the headlights (or at least the holes left by them) are the older round ones.
Answer: Late one night, Geoffrey used a covert listening device to overhear David explaining his barricade device to Janet which is how he figured it out.
How do we know Geoffrey really did use a covert listening device? They didn't mention him using one.
There was a scene of him using it when David told Janet about his barricade.