Brilliant work by Nic Williams and Fair Play for Women! 
That is so well written and well argued!
The Court Reporting issue might remain a problem though. Maybe there are Journalists and legal-beagles floating around here who could help clarify the current situation?
When a case goes to court, is information readily available to the press about the legal sex of a defendant? Or of a victim? Looking at the current Bench Book it seems unlikely in all cases.
It is not possible to rely on "gendered names" or how someone is addressed in court because the Criminal Justice System has been comprehensively ideologically captured.
The Judicial College produces the "Equal Treatment Bench Book" followed by the courts. It is beginning to look like an even worse situation than the College of Policing, since it produces policies following secret advice from people and bodies it will not name, apparently without any accountability to the public.
Judicial College
www.judiciary.uk/about-the-judiciary/training-support/judicial-college/governance/
The current edition of the Bench Book, published 3 March 2020, must have been some time in the making as there are whole sections and references that are now out of date.
"Warning over transgender guidance to judges"
The Law Society Gazette 24 February 2020
www.lawgazette.co.uk/news/warning-over-transgender-guidance-to-judges/5103196.article
"Guidance for judges on transgender issues has come under fire from solicitors in the wake of controversial court rulings. Feminist lawyers say the guidance, in the Equal Treatment Bench Book, fails to highlight conflicts between transgender and women’s rights.
The Bench Book advises that transgender defendants should be addressed by the pronouns of their choice and that ‘self-definition is the most important criteria’ (sic). At least one victim of violence by a transgender woman has been reprimanded in court for using male pronouns while describing the attack. Finding the defendant guilty, the judge refused the victim compensation, saying that when asked to refer to the defendant as ‘she’, the victim had done so with ‘bad grace’ or continued to use ‘he’.
Solicitor Harriet Wistrich, head of the Centre for Women’s Justice, has raised concerns about pronoun use in cases involving violence against women. ‘Here there is a conflict between the right of self-definition and the right of a victim, who may have been violated in the most horrendous way, to describe her material reality as she perceives it,’ she said. ‘Why is the victim’s right less important?’ " . . .
. . . "The Judicial College declined to identify the external experts and organisations that assist in training and formulation of policy. ‘It is not necessary or in the public interest to make public the names of all those involved in this work,’ it said."
(The desire for secrecy is also writ large in the section of the Bench Book on Transgender People. No doubt the Judicial College has been fed the usual misinformation about trans people being more likely to be murdered, attacked and harassed than anyone else.)
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"New edition of the Equal Treatment Bench Book launched"
3 March 2020
www.judiciary.uk/publications/new-edition-of-the-equal-treatment-bench-book-launched/
(I am sure there must be an existing Mumsnet thread on this!)
Equal Treatment Bench Book - Chapter 12 "Transgender People"
www.judiciary.uk/wp-content/uploads/2018/02/ETBB-February-2018-amended-March-2020.pdf
Some highlights from the "Overview" of Chapter 12 - my bolding:
p243
"Despite its use in current legislation, the term ‘transsexual’ is dated and some people find it stigmatising. It is preferable to use the term transgender – if it is necessary to the legal proceedings to refer to a person as being transgender at all.
The gender landscape is rapidly changing. Increasing numbers of people identify, for example, as non-binary, a-gender and gender fluid. They are also transgender within the broader meaning of the term. UK law has not yet caught up with these social changes."
"It is important to respect a person’s gender identity by using appropriate terms of address, names and pronouns. Everyone is entitled to respect for their gender identity, private life and personal dignity."
p244
Treatment of transgender people in court
"It should be possible to recognise a person's gender identity and their present name for nearly all court and tribunal purposes, regardless of whether they have obtained legal recognition of their gender by way of a Gender Recognition Certificate.
A person’s gender at birth or their transgender history should not be disclosed unless it is necessary and relevant to the particular legal proceedings.
The Gender Recognition Act 2004 (section 22) explicitly prohibits disclosure of such ‘protected information’ where a person has applied for or obtained a Gender Recognition Certificate. It makes a specific exception where disclosure is for the purpose of proceedings before a court or tribunal, but this exception should be interpreted narrowly. For more detail on section 22, see ‘Disclosure of protected information under section 22 of the Gender Recognition Act’.
In the rare circumstances where it is necessary to disclose a person’s previous name and transgender history, the court may consider making reporting restrictions to prevent the disclosure of this information, or directing a private hearing."
(Excuse me - but why all this 'effin secrecy for the statistically least vulnerable group in society and when it seems 99.9% of "transgender people" are loudly "out and proud"??)
Transgender offenders
"Transgender people are likely to be highly apprehensive about being sentenced to a term of imprisonment."
(Unlike the rest of the population?? Or because they are disproportionately likely to be sex offenders, who get a rough time in nick?)
p245
Acceptable terminology
"Using acceptable terminology avoids offending parties and witnesses and gives them confidence they will receive a fair hearing. As stated above, most individuals will find the terms ‘transgender’ and ‘trans’ acceptable, but not ‘transsexual’. Individuals who have completed a gender transition may no longer regard themselves as transgender, but simply as a man or as a woman."
(Yes, we've had that memo! It does not mean that they are though.)
Equality Act 2010
"The Equality Act 2010 appears to be limited in its protection for transgender people, in that the protected characteristic is defined as gender reassignment." [flag]
(We see you, you secret "advisors", softening up the Judiciary for that attack on the Equality Act that you have sworn Scouts Honour you have no intention of making.)
p246
"Some transgender people may be particularly concerned about their previous name and gender assigned at birth being unnecessarily revealed in court. They may also be worried about receiving negative attention from the public and the press." 
(Or individuals they have defrauded, for instance. Example plucked out of the air.)
I am losing the will to live reading the full chapter that comes after the Overview!
To return to the question in hand, which is how would a Journalist be 100% certain in 100% cases about the sex of a defendant, witness or victim?
In most cases, of course, it is bleedin' obvious, trans or not. However, it is perfectly possible, and I do wish a lot of people would stop denying it, for some men to present convincingly as women. Equally, there are some women who are able to present convincingly as men.
They do not necessarily identify themselves as transgender because, as we know, "gender identity" is all about the magical, internal, subjectively-experienced, secular-soulicious "gender essence". Neither need they wish to be perceived by others as the opposite sex. Some might not give a damn either way.
I might have misread the situation but it seems to me that judicial adherence to the Bench Book presents an insurmountable barrier to journalistic integrity in terms of the accurate reporting of the sex of persons involved in court proceedings.
The Trans Lobby might hate JK Rowling for her support for Maya Forstater but they have pulled a real stunner in fashioning a Cloak of Invisibility by Gaslight for when anyone under that "Transgender Umbrella" is up before the Beak. If Self-ID goes through, or "Gender Identity" gets written into the Equality Act, the field is wide open to abuse.
I don't suppose any of the secret advisors thought to mention to the Judicial College that there are Trans Advocacy groups arguing for the immediate release of all Trans Prisoners, pending the abolition of all prisons altogether?