By the scruff of the/somebody's neck phrase
If you say that you take, hold, grab,etc. an animal or a person by the scruff of their neck, you mean that you take, hold, grab,etc. by the back of their neck.
I took the puppy out of the mess by the scruff of its neck.
The security staff took him by the scruff of his neck and threw him out.
I wonder why mother cats pick kittens up by the scruff of the neck.
The origin of this phrase is not clear.
To be dishonest or deceptive and no one can believe
No one believes what she said. She couldn't lie straight in bed.