On the original curious question
The GRO deaths index does not show the deaths of any two Sprid* surnames in the same quarter in Cornwall, 1838 to 1930, who could be a murdered father and mother, except in 1849 when there were three burials, no ages shown: Thomas Stephen, Ruth and Susanna, in St Germans reg dist. The OPC site also has no two Sprid*s buried at the same time, but coverage is very spotty in the 1800s. Familysearch has burial images only up to 1776 for Mevagissey, so can't check details there. The OPC site has no burials for Mevagissey 1800-1900.
Only one Sprid* death was ever registered in St Austell district: Henry, aged 80, 1887.
The deaths of Thomas and Ruth Spriddle were recorded three pages apart in September quarter 1849, which might suggest they didn't die at the same time. Thos and Ruth Spridle in the 1841 census in Rame were aged c65, with a daughter Ruth aged c30. They had no male children with them in 1841, and there is only one Sprid* baptism in the OPC database with parents Thomas and Ruth: Frances 1813 Lansallos.
Susanna's death was recorded on an earlier page that quarter. There were two Sussanna Spriddles in Maker aged 13 and 14 in 1841, one not with parents (possibly with grandmother) and one the child of Elizth and Pascho.
Ah, Maker was classified as Devon (but St Germans reg dist stil) at that time in the censuses. There are Spriddles (and a couple of Spriddes) in Maker in 1841. Three groups:
Henry and Sarah aged 15 (I think it might be 25) and 13
Elizth and Pascho, aged 25, and kids
Mary and John, aged 35, and kids
There were also Spriddles in Stoke Damerel, but again, no two deaths in the same quarter. And the 1851 census shows quite a few more older Sprid*s in Cornwall than the 1841 census did (blame mistranscriptions I guess).
An internet search for
"public hangings" cornwall gives the info that public hangings were abolished in 1868 and that the last one outside Bodmin Jail in particular took place in 1862. I wondered whether hangings might have been centralized in Bodmin, but there were no Sprid* deaths registered there before 1903. All Sprid* deaths in Cornwall up to 1869 were in St Germans reg dist, save one, a woman, in Stratton in 1850.
Ah, the tales our families tell us.
But maybe there was such a fellow, he just wasn't a Spriddle! And remember, people were hanged for a lot less than murder (although probably not often by the time public hangings ended):
http://www.redpostinnholidaypark.co.uk/the-inn-and-cafe.php (near Stratton)
"A gallows stood at the cross-roads for centuries and the last public hanging in cornwall took place here for stealing sheep in the mid 1800's."
(Apparently the 1909 hanging was attended by the press, after public hangings had ended.)
Michael Barrett was the past person to be publicly hanged in Britain (Newgate Prison, London, 26 May 1868):
http://en.wikipedia.org/wiki/Michael_Barrett_%28Fenian%29