What we are dealing with is the differences between US and UK law regarding defense of self and defense of dwelling.
The laws of my state are pretty unambigious on the right to use lethal force to defend one's dwelling.
IC 35-41-3-2
Use of force to protect person or property
Sec. 2. (a) A person is justified in using reasonable force against another person to protect the person or a third person from what the person reasonably believes to be the imminent use of unlawful force. However, a person is justified in using deadly force only if the person reasonably believes that that force is necessary to prevent serious bodily injury to the person or a third person or the commission of a forcible felony. No person in this state shall be placed in legal jeopardy of any kind whatsoever for protecting the person or a third person by reasonable means necessary.
(b) A person is justified in using reasonable force, including deadly force, against another person if the person reasonably believes that the force is necessary to prevent or terminate the other person's unlawful entry of or attack on the person's dwelling or curtilage.
(c) With respect to property other than a dwelling or curtilage, a person is justified in using reasonable force against another person if the person reasonably believes that the force is necessary to immediately prevent or terminate the other person's trespass on or criminal interference with property lawfully in the person's possession, lawfully in possession of a member of the person's immediate family, or belonging to a person whose property the person has authority to protect. However, a person is not justified in using deadly force unless that force is justified under subsection (a).
(d) A person is justified in using reasonable force, including deadly force, against another person if the person reasonably believes that the force is necessary to prevent or stop the other person from hijacking, attempting to hijack, or otherwise seizing or attempting to seize unlawful control of an aircraft in flight. For purposes of this subsection, an aircraft is considered to be in flight while the aircraft is:
(1) on the ground in Indiana:
(A) after the doors of the aircraft are closed for takeoff; and
(B) until the aircraft takes off;
(2) in the airspace above Indiana; or
(3) on the ground in Indiana:
(A) after the aircraft lands; and
(B) before the doors of the aircraft are opened after landing.
(e) Notwithstanding subsections (a), (b), and (c), a person is not justified in using force if:
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(1) the person is committing or is escaping after the commission of a crime;
(2) the person provokes unlawful action by another person with intent to cause bodily injury to the other person; or
(3) the person has entered into combat with another person or is the initial aggressor unless the person withdraws from the encounter and communicates to the other person the intent to do so and the other person nevertheless continues or threatens to continue unlawful action.
(f) Notwithstanding subsection (d), a person is not justified in using force if the person:
(1) is committing, or is escaping after the commission of, a crime;
(2) provokes unlawful action by another person, with intent to cause bodily injury to the other person; or
(3) continues to combat another person after the other person withdraws from the encounter and communicates the other person's intent to stop hijacking, attempting to hijack, or otherwise seizing or attempting to seize unlawful control of an aircraft in flight.
As added by Acts 1976, P.L.148, SEC.1. Amended by Acts 1977, P.L.340, SEC.8; Acts 1979, P.L.297, SEC.1; P.L.59-2002, SEC.1.
In other words, if I have a reasonable (this is important) belief that shooting a burglar is necessary to protect my home, I am legally permitted to use that force.
The key word is 'reasonable'. It would be unreasonable for me to knowingly shoot an eight year old who wandered in the wrong house after school.
Shooting a burglar is considered reasonable in this state. In fact the county prosecutor has said flat out that he wouldn't even try to prosecute anyone who shot an intruder in their home.
Colorado's law is even better:
1) The general assembly hereby recognizes that the citizens of Colorado have a right to expect absolute safety within their own homes. (2) Notwithstanding the provisions of section 18-1-704, any occupant of a dwelling is justified in using any degree of physical force, including deadly physical force, against another person when that other person has made an unlawful entry into the dwelling, and when the occupant has a reasonable belief that such other person has committed a crime in the dwelling in addition to the uninvited entry, or is committing or intends to commit a crime against a person or property in addition to the uninvited entry, and when the occupant reasonably believes that such other person might use any physical force, no matter how slight, against any occupant. (3) Any occupant of a dwelling using physical force, including deadly physical force, in accordance with the provisions of subsection (2) of this section shall be immune from criminal prosecution for the use of such force. (4) Any occupant of a dwelling using physical force, including deadly physical force, in accordance with the provisions of subsection (2) of this section shall be immune from any civil liability for injuries or death resulting from the use of such force.
In Indiana or Colorado Tony Martin wouldn't have been charged with, much less convicted of, any crime.