On point 5 (cross examination of medical witness for baby B)
Ben Myers KC is now questioning Dr Arthurs.
He asks questions about 'air in the body' and analysis of them.
Mr Myers: "Radiographic evidence of air embolus is rare, isn't it?"
Prof Arthurs: "Yes."
"On post-mortem imaging, the presence of air may also be the result of medical procedures or placement?"
"Yes."
Mr Myers asks if the presence of a UVC or long line for some time could lead to air in the system. Dr Arthurs agrees.
Prof Arthurs says the "assumption that an image is needed to prove an air embolus is wrong".
Prof Arthurs says his review of the cases involved him, to give a conclusion of 'unusual', having to look through a number of past cases.
Mr Myers says that translated to similar findings in 25% of the total number of past cases he had gone through.
Mr Myers says Prof Arthurs looked at 500 cases at Great Ormond Street Hospital, which after narrowing down the criteria, amounted to 38 babies aged under two months, and of those, eight had gases in the greater vessels.
Prof Arthurs said there were "no unexplained cases" of gases in that location. The causes found included trauma, a road traffic accident, sudden unexpected death in infants or congential heart disease.
Mr Myers said that does not include many cases of babies in similar circumstances of death of babies aged under four days old.
He says there are "many variables" in such a study.
Prof Arthurs says air can be 'distributed' in the system during CPR.
For Child A, Mr Myers says "one possibility" of the air seen on the image is air administration.
He says others can be through resuscitation or post-mortem changes.
Prof Arthurs: "Yes."
For Child B, the radiograph image shown from June 10, about 40 minutes after the time of the non-fatal collapse.
Mr Myers: "On that image, there are no features which support an air embolus diagnosis?"
Prof Arthurs: "Yes."
He clarifies from a question by the prosecution that it could not be concluded either way.
Prof Arthurs says his observational study was from "a large body of evidence".
The judge, Mr Justice Goss, asks about the study as the jury has not seen it.
Prof Arthurs said the study was carried out for children (up to 18 years old) in 2015 and looked at 35 cases, with 10 having some gas in the larger vessels. The study was published, peer-reviewed and available in literature.
He tells the court "probably none" were of premature babies.
The study was performed independently of the trial, the court hears, and was prior to Prof Arthurs' own review, for babies, carried out later at Great Ormond Street Hospital, involving hundreds of cases.