Therefore I remain questioning the decision re murder v infanticide, and the appropriateness of the sentence.
This has been covered several times already on this thread but, for clarity, I'll explain it again. The judge had to give the jury 3 options to consider: a not guilty verdict, guilty of infanticide (which would mean that he could hand down a lighter sentence) or guilty of murder. The jury deliberated for over 8 hours and, having taken into consideration all of the evidence given to them, they decided that Mayo was guilty of murder. The verdict was theirs and theirs alone and unless you want to dispense with our judicial system of trial by jury, you'll have to come to terms with the fact that they were the ones with full visibility of all the facts and it was on those facts that they based their verdict.
The judge is given parameters of sentencing for each crime, based on the verdict given to him. He cannot just give an arbitrary sentence; every crime has a recommended sentence and he is legally obliged to follow those sentencing guidelines. The judge followed the law and if you read the sentencing notes provided by GSM earlier, you will see that he explains all of this in quite simple terms. Please read them.