Are executions necessary to deter capital crimes?

Are executions necessary to deter capital crimes? What would be a good alternative to executions to seek justice for capital crimes? 

• Two comprehensive and concise paragraphs will answer the questions properly 
• Grammar and diction are important
• Post two additional required comments to  two other students, it will promote a holistic learning approach to the topic discussed
• The class text is a good source to use to support your opinions