At the start of today’s judicial review hearing, Court 28 was packed: journalists, a few members of the public and even some of the lawyers had to grab whatever kind of seat they could. I just about managed to wedge myself in between the Bar and the BBC.

David Miranda is challenging his questioning and detention by police at Heathrow airport last August under Schedule 7 of the Terrorism Act 2000, and the seizure of data he was carrying. His case rest on three arguments: that the stop was not carried out for the proper lawful purpose; that it breached freedom of journalistic expression; and that Schedule 7 is itself incompatible in principle with free speech.

Matthew Ryder QC, for Miranda, began the day by telling the court (Lord Justice Laws, Mr Justice Ouseley and Mr Justice Openshaw) that, since a statement from the former Guardian journalist Glenn Greenwald had been put in evidence, there was no longer a dispute that some at least of the material taken from David Miranda was journalistic in nature. Steven Kovats QC, for the Home Secretary, made clear his position that he didn’t admit but neither did he any longer deny that some of the “Miranda material” was journalistic. He would, though, continue to argue that raw documents leaked to journalists by Edward Snowden were not in themselves journalistic.

How one defines “journalistic material” was a point the judges pressed both counsel on. Steven Kovats admitted he’d meant that phrase only in its natural, informal sense. But later in the hearing Matthew Ryder tried to persuade the judges that the key was the definition in section 13 of the Police and Criminal Evidence Act 1984, which he argued covered the “Miranda material” whether in David Miranda’s, Glenn Greenwald’s or even Edward Snowden’s hands.

Lord Justice Laws seemed to be leaning towards the Home Secretary’s view on this: he couldn’t see that “raw” intelligence documents became journalistic in nature simply because a journalist has possession of them. In response, Matthew Ryder QC pointed out that Glenn Greenwald, in his statement, explained that much of the material was not raw but organised and filtered by journalists for journalistic use.

Matthew Ryder made two submissions about the meaning of “terrorism” under section 1 of the 2000 Act. Together they amounted to saying that whatever terrorism does include, it can’t include responsible journalism.

First, he argued that it does not cover every action that endangers life. To be a terrorist you had, he said, to intend to endanger life or at least be reckless about it (although later he seemed to withdraw this, telling the judges by mentioning recklessness he’d perhaps conceded too much). Responsible journalism was not reckless about the risks it caused, he argued, and intended no threat to life. Openshaw J pushed back against this: section 1 creates no criminal offence, he said, so it was unhelpful to import into it concepts from criminal law such as intent. Laws LJ seemed less resistant to the argument that terrorism might need to be defined narrowly (the legal definition covering a narrower range of behaviour than it seems to, literally); he suggested section 3 of the Human Rights Act might compel a narrow reading. That’s a point that neither side has raised, and I’ll be interested if it emerges as important tomorrow.

Ryder’s second submission was that actions or threats are only caught if they directly or substantially endanger life. A responsible publication could be said to endanger life in a remote, hypothetical way by reducing national security capability at the margins, but such remote, abstract dangers were not covered. Laws LJ was not impressed by this argument: he said it was going nowhere, and that

there are better points in the case.

I thought this was a little hasty, and that the argument has some substance. Many activities increase risk to someone’s life in an indirect or remote way. An example might be reinstating a surgeon dismissed for poor performance. We wouldn’t dream of calling it terrorism if a politically motivated group were to lobby health ministers on his behalf.

Several times during the day the judges raised the question of exactly whose purpose needed to be considered when deciding whether the stop was carried our for the proper purpose – deciding whether Miranda was a terrorist – laid down in Schedule 7. Matthew Ryder for David Miranda argued that it was the purpose in the minds of the examining officers – the police officers who actually stopped and questioned his client – that counted.

The trouble was, he said, that there had been a two-stage process in which a Detective Superintendent, in dialogue with the Security Service, had authorised the stop. There was an intelligence “firewall” between him and the examining officers who actually questioned Miranda on his instruction. They did not have access to intelligence about what David Miranda might be carrying.

The result, argued Ryder, was that the examining officers were unable to conduct the Schedule 7 stop meaningfully as an independent exercise. In truth, they were influenced and guided by the Detective Superintendent whose purpose was itself tainted by the Security Service’s real aim, which was to recover whatever documents Miranda was carrying. He was the one who decided that the “Miranda material” should be detained.

Steven Kovats for the Home Secretary argued that it was the examining officers’ purpose alone which counted, and that this could be the correct statutory purpose even if the stop was done at the request of MI5.

I felt neither counsel seemed to be persuading Laws LJ on this point. He expressed the view (more than once) that what mattered under Schedule 7 was not the subjective purpose in any individual mind, but what the purpose of the stop was, objectively speaking. He saw written communications between MI5 and the police, specifically the “Port Circulation Sheet” and national security justification contained in it, as the best evidence of this. This approach differs from that taken by the parties so far (we’ve yet to hear Jason Beer QC for the police) and could lead to a finding for either, depending on what Laws thinks the dominant objective purpose was.

There was little argument on which sorts of purposes did and which did not fall within Schedule 7: but we should hear that tomorrow.

Finally, a fair part of today was taken up by the argument – relevant both to the “improper purpose” complaint and the proportionality of the interference with free expression – that the use of Schedule 7 conveniently bypassed the parallel regime under Schedule 5 which a judge to authorise police access to journalistic material. On this, the going was very tough for Matthew Ryder. He made the argument as strongly as it could have been made, I thought, but there was no sense that any of the judges was attracted to it. From what I saw today, they seem likely to agree with Steven Kovats that the two regimes are not parallel at all.

Overall, I think the defendants will be a bit happier with the day than David Miranda’s side. Matthew Ryder seemed to make less headway with the judges than he might have liked. But there’s a lot to play for tomorrow – especially on the crucial issues of purpose and how widely terrorism is defined.