There's nothing like a bullet trajectory to get a reporter's pulse racing - whatever that abstract vector did to its original target. In the first Dispatches report on the shooting of WPC Yvonne Fletcher outside the Libyan Embassy in 1984 (C4), much use was made of trajectories: independent pathologists pushed long wooden canes through anatomy class skeletons, weapons experts talked about range and velocity, and computer animations demonstrated the kind of strange contortions the victim would have had to perform in order for her wounds to coincide with that other piece of narrative geometry - the official line.

But while trajectories are very good at pointing (in this case to a building across the square), they don't name names. In a second film (the first was repeated last week), Dispatches tried to work out who actually pulled the trigger, or - this being a complicated plot of double-agents and disinformation - who allowed the trigger to be pulled. The evidence pointed to a group called Al Burkan, a privately-funded anti-Gaddafi group which had murdered Libyan diplomats and, for the sake of black propaganda, some of their own members, too. Using Berlin criminals, they smuggled handguns into London, for use in political assassinations. It was one of these weapons, the programme implied, that had been used to kill Yvonne Fletcher, and intelligence services on both sides of the Atlantic had colluded in the deed - all the parties wanted to anneal Western hostility to the Libyan government, and a flagrant act of violence was a good way to do it.

That first programme had been rather effective in arousing your suspicions, using recorded facts or demonstrable inconsistencies to make its case. But the follow-up raised questions in a less useful way. To begin with, it depended very heavily on the testimony of men whom you would not readily trust to direct you across the road. And the additional plotline, with its new cast members of malevolent Libyan millionaires and German crooks (plus a cameo appearance by that old favourite, Colonel Ollie North) made the story less rather than more plausible.

The implication was that British Intelligence had allowed Al Burkan members access to a nearby building, and suppressed an intercepted Libyan cable which warned that gunfire might be used against the demonstrators. But this sounded a very haphazard enterprise, dependent on lightning reflexes and a sniper's eye. If they were going to risk an extra shot (which would have to be timed as closely as possible with any burst of gunfire from inside the embassy), would they really have used a handgun with a homemade silencer, a weapon which is hardly the last word in accuracy? In any case, if they knew there was going to be shooting from within the embassy, why take the extra risk at all? Why not simply rely on their natural talent for arousing outrage? The talk earlier had been of "compelling evidence" but the end result was something much more confusing.

ITV's 3-D included an unsettling report on plastic surgery for Down's syndrome children, a rather drastic solution to social prejudice, or possibly tinged in some cases with parental concern for the aesthetic. "If we can dilute the obvious features of Down's syndrome and reduce the possibility of teasing or bullying at school, it's well worth it," argued the plastic surgeon who performs the operations. There are two responses to this, the first being that social prejudice should change rather than children's faces (and while it is much harder to do the former, it will be a great deal more difficult if all visible signs of human difference are hidden away like this). Secondly, that it was unlikely to work anyway. The surgery cannot affect the brain, and children's cruelty clings to behaviour just as efficiently as it does to looks, indeed, it might even be liberated by the outward appearance of normality. I wouldn't casually pass judgement on parents who have had to come to terms with such circumstances, but you were left musing on how great the distress would have to be before you would subject a three-year-old child to surgery of the tongue.