Two people have had their convictions over "shaken baby" cases quashed and another has been reduced.
The Angela Cannings case raised questions about expert evidence
Four people appealed against convictions secured on the basis of medical experts' evidence.
Lorraine Harris, 36, had her conviction for manslaughter quashed, while Michael Faulder, 34, had his conviction for grievous bodily harm overturned.
Ray Rock's murder conviction was reduced to manslaughter. Alan Cherry had his appeal dismissed.
Cherry had been convicted of manslaughter.
Rock was given a new sentence of seven years, and as he has already served six, his lawyer said he was likely to be released on Thursday.
Ms Harris had served her sentence and been released already, but lawyer Campbell Malone said she was still suffering the terrible consequences of her conviction.
She was unable to go to her baby's funeral and had a baby she gave birth to as she was starting her sentence taken away for adoption.
Lord Justice Gage, sitting with Mr Justice Gross and Mr Justice McFarlane in London, agreed that the presence of the three typical symptoms of "shaken baby syndrome" did not automatically mean that a crime had been committed.
But the panel did insist that the "triad" of injuries had not been undermined in the way the defence suggested and remained valid, with limitations.
In all of the four cases experts told jurors the victims' injuries showed they had been violently treated, despite a lack of any other evidence.
These injuries were swelling of the brain, bleeding between the brain and skull and bleeding in the retina of the eyes.
But at the Court of Appeal in June, lawyers argued medical opinion had changed, making the convictions unsafe.
New research since 2001 had led to a reappraisal of these symptoms, the Court of Appeal heard.
Lawyers presented fresh evidence that the same injuries could be caused by children falling from a relatively low height.
They might also be linked to vaccinations or medication, could result from a difficult birth or have genetic causes, the court heard.
Rock's victim's mother, Lisa Davis, left the court in tears after his conviction was reduced.
"I am devastated. What they are basically saying is that you can shake a baby to death and you are not guilty of murder. You only get manslaughter."
Rock's mother, Linda Rock, said: "I was hoping for him to be cleared 100%, but that was a bit too much. I got 50% and will have to be happy with that."
Mr Malone, who also represented Cherry, said he would continue the fight to clear his name.
Responding to the ruling, the Crown Prosecution Service said in a statement: "Today's judgment sends a clear signal validating the approach used by the CPS in prosecuting shaken baby syndrome cases.
"The judgment was also about individual cases - two convictions were upheld (one of which was reduced from murder to manslaughter) and two quashed on unrelated new evidence particular to the facts of each case."
The four appeals were by:
Raymond Rock, of Great Yarmouth, Norfolk, serving life for murdering his girlfriend's 13-month-old daughter, Heidi Davis, in 1998.
He was alleged to have shaken the child violently but he insisted she wriggled out of his arms and fell to the floor.
Lorraine Harris, 36, of Long Eaton, Derbyshire, jailed for the manslaughter of her four-month-old son, Patrick McGuire, in 2000.
She said the baby became ill and stopped breathing after a vaccination. He had a blood disorder which was only discovered after his death.
Ms Harris has been released from prison but is banned from seeing her other child.
Alan Cherry, convicted at Birmingham Crown Court in 1995 of the manslaughter of his girlfriend's 22-month-old daughter, Sarah Eburne-Day.
He denied shaking her in a fit of temper, claiming she fell off a stool she was standing on. He is no longer in custody.
Michael Faulder, 34, of Gateshead, jailed for two-and-a-half years at Teesside Crown Court in 1999 for causing grievous bodily harm to a seven-week-old boy.
He said he accidentally dropped the baby while trying to put him into his pushchair. The child made a full recovery.
The appeals have been seen as a test case on the reliability of expert evidence used to establish shaken baby syndrome in the past.
More than 90 other convictions could eventually be challenged.
It could also affect hundreds of Family Division cases in which a parent - usually the father - has been denied access to their children on the basis of alleged violent treatment.
The appeals result from a review ordered by Attorney General Lord Goldsmith following the successful appeal by Angela Cannings against her conviction for murdering her two baby sons.