% !TeX TXS-program:compile = txs:///pdflatex

\documentclass[margin=5mm]{standalone}
\usepackage{tikz}
\usetikzlibrary{shapes.misc}
\tikzset{cross/.style={%
		cross out, draw=black, minimum size=2*(#1-\pgflinewidth), inner sep=0pt, outer sep=0pt},
	cross/.default={1pt}}
\begin{document}

\begin{tikzpicture}[line join=round]
	%points
	\coordinate (A) at (0,0) ;
	\coordinate (B) at (6.2,0) ;
	\coordinate (C) at (3,-2) ;
	\coordinate (D) at (-3.2,-2) ;
	\coordinate (S) at (1.5,2.8) ;
	\coordinate (I) at (1.5,-1) ;
	\coordinate (K) at (-0.85,0.4) ;
	\coordinate (L) at (2.25,0.4) ;
	\coordinate (M) at (3.85,1.4) ;
	%traits
	\draw[very thick] (S) -- (B) -- (C) --(S) -- (D) -- (C) ;
	\draw[very thick,dashed] (D) -- (A) -- (S) (S) -- (I) (A) -- (C) (D) -- (B) (A) -- (B) ;
	%labels
	\foreach \Point/\Pos in {A/above left,B/right,C/below,D/left,S/above,K/above left,L/above right,I/below,M/above right} \draw (\Point) node[\Pos] {\Point} ;
	\foreach \Point in {K,L,M} \draw[very thick] (\Point) node[cross=3.5pt,blue] {} ;
\end{tikzpicture}

\end{document}