The law governing how the justice system deals with children who commit offences is laid down in the 2001 Children Act.
The State is also guided by the "Beijing rules" on the administration of juvenile justice adopted by the UN General Assembly in 1985.
Another influencing factor is the 1999 decision of the European Court of Human Rights (ECHR) in relation to the two boys convicted of the murder of toddler Jamie Bulger in the UK in 1993.
The ECHR found Robert Thompson and Jon Venables, who were 11 at the time, and tried in public in an adult court, did not get a fair trial.
The Irish legislation does not expressly deal with children who commit the most serious crimes on the statute books. Adults who are convicted of murder are given a mandatory life sentence. This does not apply to children, although there is no express ban on a judge imposing a life sentence on a child in the circumstances of a particular case.
The 2001 Act sets out some of the principles that apply to the sentencing of children.
It says any penalty imposed on a child for an offence should cause as little interference as possible with the child's "legitimate activities and pursuits" and should take the least restrictive form that is appropriate in the circumstances.
In particular, it says "a period of detention should be imposed only as a measure of last resort".
It specifies that children under 18 may not be imprisoned. Instead the court must make an order imposing a period of detention on a child, only if satisfied this is the only suitable way of dealing with him or her.
Normally the detention period for a child should be no more than three years. But in the case of those convicted of more serious offences, a longer period can be imposed. This sentence must be served in a detention centre initially. When the child turns 18, they can be transferred to prison to serve the remainder of their sentence.
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This case has been described by legal sources as "unprecedented", "complex" and "challenging" and by the judge himself as "unusual".
Mr Justice Paul McDermott said after the boys' conviction that he was seeking "professional assistance" in sentencing.
Probation reports as well as psychiatric and psychological assessments have been prepared in respect of each of the two boys.
The court heard victim impact statements from the Kriégel family and the judge also heard from the grandfather of Boy A.
The Kriégel family prepared their statements in the aftermath of the teenagers' convictions for murder but had asked that all the evidence be heard together.
Mr Justice McDermott has made it clear that he considers the physical and mental well-being of the two convicted boys to be "paramount" in relation to how he conducts the sentencing.
At a hearing last week, he pointed out that what he decides is likely to be the most significant decision a third party will make in their lives. And he said this would create huge pressure for an adult, let alone for young, vulnerable children.
He said that when a decision of such magnitude was made, it was likely the children would require immediate support from their parents in circumstances that "may involve enormous emotion". And he said the court was obliged to afford them a certain degree of decency and respect.
To this end, the judge ordered that only five journalists were to be present in the courtroom. Others were accommodated in an adjacent room which was set up with a live feed of the proceedings. Because of the age of the convicted boys, the hearing is not open to the public.
As such cases are rare, there are not many precedents for sentencing children for murder.
In 1998, Mr Justice Paul Carney sentenced a teenage girl to seven years' detention for the murder of chip shop owner Franco Sacco in Templeogue in 1997. The girl was 15 years old at the time of the murder.
The most recent comparable case is that of DG who was convicted in 2004 of the murder of 14-year-old Darragh Conroy. The boy was 15 at the time of the murder and was named during the trial, due to a loophole which allowed juveniles tried in courts other than the Children's Court to be identified.
The law has since been amended.
He pleaded not guilty and was convicted by a jury. Mr Justice Barry White sentenced him to be detained for life, for a "premeditated, brutal, vicious and callous" killing but ordered that the sentence be reviewed by the Central Criminal Court after ten years.
The sentence was appealed both by the boy's lawyers and by the DPP but was upheld by the then Court of Criminal Appeal. The court found the trial judge was correct to impose a life sentence subject to review.
It also found that there was a "special onus" on the court in relation to children convicted of serious offences, which would normally involve lengthy custodial sentences, to have regard to their rehabilitation and welfare for the future.
The sentence was reviewed in 2014 and the boy was released less than two years later.
Today's sentencing has been adjourned until next Tuesday.
