How does the point of view create a suspenseful mood in "Lamb to the Slaughter" ?

This is a very good question. The story is told entirely from Mary Maloney's point of view. The reader identifies with her because we are held in her point of view from beginning to end. Early in the story we understand her emotions. She is in love, she feels content, and she is six months pregnant. We wish her well. After she commits her murder she has to call the police. Since we are held in her point of view, we cannot know what the police are going to do or what they are going to think. When she goes to the grocery store to establish an alibi, she is still improvising. She knows she has to go back home and pretend to find her husband's body, then call the police and pretend to be in panic and shock, and then to put on an act of innocence and mourning while police swarm all over her house and one or two of them ask her questions. She doesn't know what kinds of questions they might ask. She doesn't know what they might suspect--or even what they might know about Patrick that she doesn't know.

It is because we are held in her point of view that we share her suspense. She is trying to get by with murder, but she doesn't know whether or not she is going to succeed. She knows that it is very hard to get by with murder, and she knows that spouses are often prime suspects. She has to keep her cool. She has never played this role before. That is why so many murderers get caught. They overact. They don't know how to play the part. Mary knows she must be bereaved but not too bereaved. How do women act when their husbands are murdered? Maybe they simply act as if they are in a state of shock and do not show much emotion?

It is a very nice touch that Mary wants to go on about her daily routine, which at this time of day involves cooking a leg of lamb. It seems natural for some people to be in a state of denial and to want life to go on just as it had been going on before. She could play that role rather than acting as if she were totally overwhelmed and incapacitated. After all, she is a cop's wife. She knows her husband faces danger every day. He would expect her to be tough. These cops who have invaded her home are all Patrick's buddies. She would be expected to show them some hospitality in spite of her suffering. She is never entirely safe. She never knows what is going to happen next. In making the radical decision to murder her husband, she was entering into a strange new world.

A parallel example is Rodion Raskolnikov in Fyodor Dostoevsky's novel Crime and Punishment. He intends to murder one woman. Another woman shows up unexpectedly and he has to murder her too. Then he can't get out of the murdered women's apartment because a group of people has collected outside in the hallway. When he does manage to get away, he has to worry about the police investigation. He is under a strain throughout the novel, and the reader, held in Raskolnikov's point of view, suffers the strain along with him.