\documentclass{standalone}
\usepackage{luamplib}
\begin{document}
\begin{mplibcode}
def freehand_segment(expr p) =
 point 0 of p {direction 0 of p rotated (4+normaldeviate)} ..
 point 1 of p {direction 1 of p rotated (4+normaldeviate)}
enddef;
def freehand_path(expr p) =
 freehand_segment(subpath(0,1) of p)
 for i=1 upto length(p)-1:
   & freehand_segment(subpath(i,i+1) of p)
 endfor
 if cycle p: & cycle fi
enddef;
defaultfont := "eurm10";
color sepia; sepia = (0.44, 0.26, 0.08);
picture marker; marker = image(for s=-1/2, 1/2:
 draw (left--right) scaled 2 rotated 60 shifted (s,0);
endfor);
def moved_along expr x of p =
 rotated angle direction x of p
 shifted point x of p
enddef;
beginfig(1);
 pair A, B, C, D;
 A = (0,-30); B = (180,0);  C = (120,90);
 D = (1/2 + 1/40 normaldeviate)[A, B];
 path triangle, circumcircle, bisector;
 triangle = freehand_path(A--D--B--C--cycle);
 bisector = freehand_segment(C--D);
 circumcircle = freehand_path(A..B..C..cycle);
 draw triangle;
 draw bisector;
 draw circumcircle withcolor .67 red;
 draw marker moved_along 1/2 of triangle withcolor .67 red;
 draw marker moved_along 3/2 of triangle withcolor .67 red;
 label.lft("A", A);
 label.rt ("B", B);
 label.top("C", C);
 label.bot("D", D);
endfig;
\end{mplibcode}
\end{document}