各位老师好，我在阅读《哈利波特与火焰杯》时读到一个句子：
he killed them, and I don’t care what the police say,” said Dot in the Hanged Man. “And if he had any decency, he’d leave here, knowing as how we knows he did it.”
请问这个句子中的“knowing as how we knows he did it”的结构是什么？as在句中起什么用途？
as how为地方性用语，仅用于非正式场所，引导名词性从句，等于that。容易见到于少数动词之后，如allow，know，say, seeing等。
《美国韦氏词典》
As how 连词:=that
she allowedas howshe was glad to be here
《朗文英语词典》
seeing as informalused before giving a reason for what you are saying
‘I might as well do something useful, seeing as I’m back,’ she said.
Well,seeing ashow you just lost one of your men, you might think abouthiringsome one toreplace him.
The man came, measured the height and girth of the tree, and allowed as how this was one of the most firmly rooted junipers hed ever seen.
She didnt know I had sent it to her ... but she allowed as how she liked the book.
I dont know as how your father will like that.
小说中作者为了让读者知道人物的性格特点和受教育程度，常在对话中保留人物的说话时的语法错误。we knows就是一个例子。
