Idiom- someone looks and acts as if they're innocent?

Question

Often people will pretend that they are totally innocent just to get other people to be claimed as guilty. They will not take accountability for something that occurred or their mistakes. How do you tell if they are this kind of person based off of the way they are talking or using their English?

Second part, What is an idiom that could be used to describe this kind of person? I am writing a story with a character like so in it.

Here's my assumption of what that idiom would be:

He's Just a blind seeker.

I'm not sure if that's accurate or even a real official idiom.

Answer 1

I've only known the expression

[he looks as though] butter wouldn't melt in his mouth

to be used when referring to someone who is good at dissembling.

Although other reference works give a less pejorative sense, Cambridge Advanced Learner’s Dictionary & Thesaurus only gives this sense:

used when someone ​looks as if they would never do anything ​wrong, ​although you ​feel they might:

Tommy ​looked as if butter wouldn't ​melt in his ​mouth.

Answer 2

You might say such a person is "feigning innocence or ignorance", "playing dumb or innocent", or "acting naive"

You might want to take a look a this related post, Idiom/phrase which means “to pretend not to understand or know”

As to the first part of your question, if you could come up with a definitive answer to that which could be broadly applied to all people, you could make a lot of money off of it. If you're trying to figure out how to write such a character, you'll probably need to determine what particular "tells" that specific person has when he or she is being dishonest. You could get some ideas by researching common tells when someone is lying.

Answer 3

Consider sail under false colors and [not] show one's true colors

sail under false colors: To behave deceptively; the “colors” of a ship are its identifying flags: It turned out that the door-to-door sales rep was sailing under false colors and was actually a swindler (The American Heritage Dictionary)

show one's true colors: reveal oneself as one really is, as in We always thought he was completely honest, but he showed his true colors when he tried to use a stolen credit card. (The American Heritage Dictionary)

Answer 4

For your first question- that's a very difficult one to answer if you're thinking that there are words that only a liar might use.

Determining phony behavior is more about how you say your words and less of what you say. Hopefully that makes sense. If you're interested in figuring out if someone is lying about something like being innocent, there are some resources on youtube that go into the sort of body language that liars tend to use.

For your second question, here's an idiom I think you'll like- a wolf in sheep's clothing

It comes close to your definition although the "wolf" isn't necessarily a liar/ someone who won't take responsibility, but a bad person in general.

Here's the full definition of the idiom if you are unfamiliar with it:

someone or something that ​seems to be good but is ​actually not good at all

From The Cambridge Online Dictionary

Answer 5

Your first question is difficult to answer. A lie detector engineer or a psychiatrist might give you some clues.

As for your second question, I can't come up with an idiom, but I suggest the following single words to describe that kind of person: "false" or "phony"

• false - (adj) - not faithful or loyal : treacherous: hypocritical.

e.g. "I never thought he could be such a false friend."

"phony".

• phony (adj) - not honest or sincere : saying things that are meant to deceive people

e.g. I don't think she really means to help us. She is so phony!

If you are looking for a noun, I suggest "a sham" or a phony.

• sham (noun) - "someone who deceives people by pretending to be a particular kind of person."

e.g. "Many people believed he could help them, but I knew he was a sham."