Question

Which poetic technique does Robert browning use in this excerpt from my last duchess

Answer 1

The poetic technique that Robert Browning used in his poem "My Last Duchess" is enjambment. 
That technique means that the thought found in one line of the poem does not end with the end of that line, but rather continues into the following line. There are no harsh endings of thought at the end of one line.

Hope this helps :)