No. This law was repealed in 1973 and no longer exists.
Until 1973, killing a person caught having sex with your spouse may have been legally "justifiable." At the time, Article 1220 of the old Texas Penal Code stated:
Homicide is justifiable when committed by the husband upon one taken in the act of adultery with the wife, provided that the killing takes place before the parties to the act have separated. Such circumstance cannot justify a homicide where it appears that there has been, on the part of the husband, any connivance or assent to the adulterous connection.
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