Does the 5th (6th) commandment specify murder?

I got in a short debate with a Baptist over the word used in Exodus 20:13 (12) as to whether the word used there specifically and exclusively means "murder"?

לֹא תִרְצָח--Exodus 30:13 (12)

Thou shalt not murder/kill (תִרְצָח tir'tzach) -Exodus 20:13 (12)

 Though in the 10 commandments its most reasonable to assume it is talking about murder, since that is a capital offense.  We see from this lexicon meanings of the word H7523 רָצַח:

1) to murder, slay, kill

a) (Qal) to murder, slay

1) premeditated

2) accidental

3) as avenger

4) slayer (intentional) (participle)

b) (Niphal) to be slain

c) (Piel)

1) to murder, assassinate

2) murderer, assassin (participle)(subst)

d) (Pual) to be killed

 The word does not only refer to murder as we see in Deuteronomy 19:3-4 (forgive bad punctuation its not easy to copy and paste a whole paragraph of Hebrew, the word "kill" or "murder" רֹצֵחַ rotzeach.)   

תָּכִין לְךָ הַדֶּרֶךְ וְשִׁלַּשְׁתָּ אֶת-גְּבוּל אַרְצְךָ אֲשֶׁר יַנְחִילְךָ יְהוָה אֱלֹהֶיךָ וְהָיָה לָנוּס שָׁמָּה כָּל-רֹצֵח

You shall measure the distances and divide into three parts the area of the land that the Lord your God gives you as a possession, so that any manslayer [rotzeach רֹצֵח ] can flee to them.-Deuteronomy 19:3

 וְזֶה דְּבַר הָרֹצֵחַ, אֲשֶׁר-יָנוּס שָׁמָּה וָחָי: אֲשֶׁר יַכֶּה אֶת-רֵעֵהוּ בִּבְלִי-דַעַת, וְהוּא לֹא-שֹׂנֵא לוֹ מִתְּמֹל שִׁלְשֹׁם 
“This is the provision for the manslayer [הָרֹצֵחַ harotzeach] , who by fleeing there may save his life. If anyone kills his neighbor unintentionally without having hated him in the past-"-Deuteronomy 19:4
 

 Verse 4 is significant since it speaks of the killer as a rotzeach as "unintentionally"/"without knowledge" ( בִּבְלִי-דַעַת  biv'li da'at) killing his neighbor! Is this murder? Certainly not, since it was done accidently and with no hatred! However, the word rotzeach is still used! Deuteronomy 19 continues on and give an example of killing someone by accident (the split of an axe) that flies and whacks--fatally wounding someone. This is called "manslaughter" in some translation, even though the word is "rotzeach."

We can go on to Numbers 35 for more examples of rotzeach being used for accidently killing someone, not murder.  Numbers 35:11 says

וְהִקְרִיתֶם לָכֶם עָרִים, עָרֵי מִקְלָט תִּהְיֶינָה לָכֶם; וְנָס שָׁמָּה רֹצֵחַ, מַכֵּה-נֶפֶשׁ בִּשְׁגָגָה

then ye shall appoint you cities to be cities of refuge for you, that the manslayer [רֹצֵחַ rotzeach] that killeth any person through error may flee thither.

 "Through error" show that that "rotzeach" did the crime by accident! Not murder. The word rotzeach is also used in this chapter from verses 25-31 for BOTH murder and accidental homocide.

Conclusion: The word used in the 5th or 6th commandment can depending on the context (not the word itself) refers to murder OR accidently killing someone.