The Death Penalty has always been a controversial topic, but it's become even more controversial nowadays, during the post-9/11 era that we're now going through.  There are people on the Left as well as the Right who believe that the death penalty should be used in certain cases, such as a first-degree murderer, a terrorist, or even a real deviant such as Winston Moseley, the serial killer who was tried, convicted and imprisoned for the horrific murder/rape of Kitty Genovese back in March 1964, as she was returning home from her job as a bar-girl in Kew Gardens (Queens), NY, at around three o'clock in the morning.  

However, even in cases like that, applying the death penalty to deviant criminals like the ones mentioned in the above paragraph, creates a loophole, which would eventually open up the opportunity to apply the death penalty to many more crimes, even ones that don't involve murdering a person.  Hey...I know that terrorists won't hesitate to go out and kill people to promote their cause(s), and a first-degree murderer shouldn't be out walking the street, but a life-time term, without parole,  in a State or Federal penitentiary would be a far better way to go about serving justice in such cases, if one gets the drift.

Now for the crux of the matter:

The death penalty is not a solution for the following reasons:

A)  A society that wishes to become civilized does not solve the problem by putting the perpetrators of heinous crimes to death.

B)  The death penalty creates a whole new set of victims.  Even the perpetrators of the crime(s) for which they've been executed have loved ones and friends who grieve for them when they're gone.

C)  All too often, mistakes are made.  People are often killed who turn out to be innocent of the crime for which they've been executed, the person who actually committed the crime is later found, and often ends up getting off scott-free.

D)  The death penalty is all too often used as a discriminatory tool.  Very poor people, particularly non-whites, are much more likely to end up on Death Row, and to be executed for their crimes.

E)  The death penalty is no more a deterrent to murder than life imprisonment.  The chances are better than not, imo, that if a criminal is that hardened, s/he will not stop to weigh the consequences of his or action(s).  

F)   Many prison inmates, especially those who've had to dig the grave(s) of executed inmates and help with their burials, have reverted back to much worse behavior and more aggression after being traumatized by witnessing such a horrible event.

G)  Many ministers and priests who've presided over the funerals/memorials of executed inmates have become so profoundly depressed afterwards that they've felt compelled to quit the religious life altogether.

H)  No matter how heinous a crime a person has committed, there's always a (remote) possibility for rehabilitation.  Once a life has been taken, however, it cannot be given back.

I)  How can it be said that it's against the law to go out and kill somebody when the state does precisely that?  It's hypocritical and horrifically ironic, to boot.

J)  In societies where the death penalty is used, the overall quality of life is coarsened and cheapened, the crime rates go way up, as opposed to going down,  war is rampant, family break-ups are much more common, and the overall morale of a society is sapped.

K)  When the death penalty is implemented and applied, it puts a society down to the same level of brutality as the criminal who committed the crime for which they've been executed.