der Stecher
stabber
A person who injures or kills another person with a stabbing weapon.
Die Polizei konnte den Stecher kurz nach der Tat festnehmen.
The police were able to arrest the stabber shortly after the crime.

stabber / biter / engraver
Loading your saved state.
stabber
A person who injures or kills another person with a stabbing weapon.
Die Polizei konnte den Stecher kurz nach der Tat festnehmen.
The police were able to arrest the stabber shortly after the crime.

All meanings of 'der Stecher' derive from the verb 'stechen' (to stab, sting, or prick). The suffix '-er' forms a noun that can refer to a person (perpetrator, artist), an animal (insect), or a tool (part of a weapon) that performs the action of stabbing, stinging, or pricking.
Eine Wespe ist ein Insekt, das stechen kann.
A wasp is an insect that can sting.
You can almost always recognize the meaning of 'Stecher' from the context. If it is about crime, it refers to the perpetrator. In nature, it means insects; in art, an engraver; and in shooting, a part of the weapon.
Der Jäger nutzte den Stecher für einen präzisen Schuss.
The hunter used the set trigger for a precise shot.
In connection with a crime, 'der Stecher' is often used with verbs such as 'suchen' (to look for), 'identifizieren' (to identify), 'fassen' (to catch), or 'festnehmen' (to arrest).
Die Polizei hofft, den Stecher bald identifizieren zu können.
The police hope to be able to identify the stabber soon.
The term 'Stecher' for a mosquito or another stinging insect is colloquial. It is often used when someone is annoyed.
Mach das Fenster zu, sonst kommen die ganzen Stecher rein!
Close the window, otherwise all those biters will come in!
In the meaning of a trigger mechanism, 'der Stecher' is a technical term from the language of hunters and sport shooters. Outside this context, you will hardly ever hear this meaning.
Er erklärte mir die Funktion des Stechers an seinem Jagdgewehr.
He explained the function of the set trigger on his hunting rifle to me.
deduction / trigger / withdrawal
'der Abzug' and 'der Stecher' can both refer to parts or functions of a firearm. 'der Abzug' is the normal mechanism you operate to fire a shot. 'der Stecher' is a special trigger mechanism that makes the trigger especially light and precise. The words can be confused because 'Stecher' in this sense also has to do with the trigger. In general, however, you say 'Abzug'. 'Stecher' only fits for this particular technical device.

Bei diesem alten Gewehr ist der Stecher sehr empfindlich eingestellt.
On this old rifle, the set trigger is adjusted to be very sensitive.
Der Sportschütze legt den Finger vorsichtig an den Abzug.
The sport shooter carefully places his finger on the trigger.