This is one of McBain's Matthew Hope/Florida novels, a second series other than the 87th Presinct ones. This series is about as good as the other one and I have enjoyed them all.
From back of book:
It is Christmas in Florida. The decorations are only slightly more false than the cheer, and a trial is going on--the kind of trial that grabs headlines and makes people wonder what kind of person could possibly represent the defendant. In this case, the accused, Mary Barton, is charged with killing and burying three innocent young girls.
Defense attorney Matthew Hope believes the eccentric Mary Barton would never harm a soul. So does the beautiful Englishwoman footing the bill for her defense. But all the money in the world can't buy Hope a case. The evidence for a conviction is overwhelming, and Mary, stubbornly contrary, only makes things worse. Hope wants the truth. Yet when it surfaces, it will show him just how much he has to lose--and unearth a few long-buried secrets that refuse to die.
Publishers Weekly
Three young girls are unearthed in the backyard of eccentric gardener Mary Barton in attorney Matthew Hope's 10th outing. Mystery Guild main selection in cloth.
It is Christmas in Florida. The decorations are only a slightly more false than the cheer; and atrial is going on--the kind of trial that grabs headlines and makes people wounder; what kind of person could possibly represent the defendant. In this case, the accused Mary Barton, is charged with killing and burying three innocent young girls.